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Developing and testing a new generation of protective coatings for outdoor bronze sculpture
Abstract
Outdoor bronze sculpture is vulnerable to acid rain-induced corrosion and the present protection schemes utilized by conservators do not provide adequate protection under many circumstances. To replace the current most common clear bronze protection systems, wax or Incralac® with a top coat of wax, work is underway to develop different options for conservators that include new longer-lasting, more durable systems having improved corrosion protection. The use of improved matrix binders based on fluorocarbon polymers, the use of nano-sized TiO2 for UV absorption, and the extended use of UVAs and HALS are under examination in a search for improved UV resistance and longer lived corrosion protection in clear bronze coatings. Advanced spectroscopic and electrochemical methods are being used to characterize new coatings candidates with respect to UV resistance and corrosion resistance.
... The composition and binding of the protective coating can also be determined with XPS spectroscopy. 1 Since, in essence, patination is a form of corrosion, many different coatings have been studied over the years, with the desire to retain the colours of an artefact while simultaneously protecting it. 8 The coating most commonly used within the field of conservation is Incralac, which is composed of Paraloid B-44 with a BTA inhibitor, 9,10 and has been reported to deteriorate over time. 9,11,12 The use of different fluoropolymers and waxes has also been explored, 9,[13][14][15] and different inhibitors can also be added. ...
... 8 The coating most commonly used within the field of conservation is Incralac, which is composed of Paraloid B-44 with a BTA inhibitor, 9,10 and has been reported to deteriorate over time. 9,11,12 The use of different fluoropolymers and waxes has also been explored, 9,[13][14][15] and different inhibitors can also be added. 15,16 It is, however, important to be aware of a potential change in the colour following the application of a coating. ...
... 8 The coating most commonly used within the field of conservation is Incralac, which is composed of Paraloid B-44 with a BTA inhibitor, 9,10 and has been reported to deteriorate over time. 9,11,12 The use of different fluoropolymers and waxes has also been explored, 9,[13][14][15] and different inhibitors can also be added. 15,16 It is, however, important to be aware of a potential change in the colour following the application of a coating. ...
The surface of bronze undergoes changes when it is exposed to a polluted atmosphere, and bronze should therefore be protected from this natural deterioration. The most common protective coating currently in use is Incralac, which includes toxic components and is reported to dissolve a few months after application. This work therefore investigates a fluoropolymer-based coating (FA-MS), and compares it to the protection offered by Incralac. Bronze samples (non-patinated, sulphide-patinated or chloride-patinated) were exposed to simulated urban rain for four months. The corrosion products formed were characterised using SEM/EDS and Raman analyses. To study the protection efficiency of the newly developed fluoropolymer coating (FA-MS) and Incralac protection, various electrochemical methods were used: measurements of open circuit potential linear polarisation and potentiodynamic measurements. Findings show that the FA-MS coating provides a protection efficiency of 71 % for chloride-patinated bronze and 99.5 % for sulphide-patinated bronze. Contact angles of the FA-MS samples were higher than those of the unprotected samples or the samples protected by Incralac, indicating better hydrophobic properties of the FA-MS coating.
... Fluoropolymer based coatings on bronze were investigated back in 2003 [12]. These particular coatings were tested on bare bronze as a new protective coating for the use on outdoor bronze monuments. ...
... Tests were performed on Incralac in different combinations of waxes and coatings based on hydrophobic fluoro-organic polymers. It was reported that microbes could biodegrade the Incralac finish [12]. On the other hand, in the case of fluoropolymer coatings, apart from good protective properties, the lack of adhesive properties was addressed as the main drawback of such polymer coatings [12]. ...
... It was reported that microbes could biodegrade the Incralac finish [12]. On the other hand, in the case of fluoropolymer coatings, apart from good protective properties, the lack of adhesive properties was addressed as the main drawback of such polymer coatings [12]. The recent report on comparison of performance of protective coating for outdoor bronze included, beside multiple traditional and innovative coatings, fluoropolymer coating on bare and patinated bronze and by the use of benzotriazole as the pretreatment [13]. ...
Bronze reacts with oxygen, humidity, and pollutants in the atmosphere so that a patina forms. Natural exposure to an outdoor atmosphere can be simulated and accelerated in order to achieve a patina that mimics outdoor ancient patina. In order to avoid the uncontrolled dissolving of either the natural or artificially formed patina, protection of the patina is needed.
In this study, a multi-component fluoropolymer based coating for the protection of bronze patina was developed. In order to provide various functionalities of the coating (such as the hydrophobicity of the coating surface, obtaining interactions within the coating itself as well as a bronze substrate and inhibiting the corrosion processes), a fluoroacrylate coating with appropriate adhesion promoter was suggested, with and without a silane modified benzotriazole inhibitor. The protective efficiency and durability of the applied coatings were investigated electrochemically using potentiodynamic tests and electrochemical impedance spectroscopy in a simulated acid rain solution. All of the developed coatings showed a significant decrease in the corrosion current density. The self-assembled single layer coating (FA-MS) also showed 100% inhibition efficiency. After ageing the coating remained transparent and did not change by UV exposure and/or thermal cycling. The patina and coating investigations using FIB-SEM and EDX showed that the latter coating (FA-MS) successfully covered the surface of the patinated bronze. The mechanism of the bonding was proposed and supported with the spectroscopic observation of a thin and even coating.
... the most used artificial protection of bronze objects, research into other possible protections remains active. Reports range from the use of organic protective films with inhibiting properties [3,4] and chitosan [5] to various coatings made via sol-gel [6] or prepared from formulations of polymeric resins (methyl methacrylate [7], polyurethanes [8] and fluoropolymers based on polyvinylidene fluoride (PVDF) [4]). ...
... the most used artificial protection of bronze objects, research into other possible protections remains active. Reports range from the use of organic protective films with inhibiting properties [3,4] and chitosan [5] to various coatings made via sol-gel [6] or prepared from formulations of polymeric resins (methyl methacrylate [7], polyurethanes [8] and fluoropolymers based on polyvinylidene fluoride (PVDF) [4]). ...
... Although fluorocarbons and hydrocarbons have different properties and express phase separation behaviour in some mixtures [9], the direct bonding of −CH 2 -CF 2 -units to PVDF enables the formation of a semicrystalline polymer with an extended zigzag chain. When PVDF is used for the protection of bronze, the dispersion of pigments and adhesion is not sufficient [4]. Consequently, physical mixing with acrylic modifiers was attempted, but adhesion only increased from poor to average [4]. ...
Solvent- (SB) and water-borne (WB) fluoropolymer coatings were produced for the outdoor protection of bronze. The coatings were prepared from commercially available resins with alternating fluoroethylene/vinylether copolymers. Because any application of protective coatings on works of art requires that they be removable in accordance with conservation ethics, various approaches to achieve removability of coatings were tested. The influence of modifications was verified through comparisons of hydrophobic, compact and irremovable protective coatings. Consequently, we prepared four types of coatings: two SB coatings and two WB coatings. The first SB coating was designed to have a hydrophobic compact structure (SB-c coating), and the second SB coating was modified with the addition of agents that impart strippability (SB-h coating). The same approach was used for the preparation of the two WB coatings: a compact (WB-c) coating vs. a hydrophilic (WB-h) coating, the latter being prepared through the addition of hydrophilic polyisocyanate.
The surface properties of the coatings were compared using scanning electron (SEM) and atomic force (AFM) microscopy. WB coatings were found to be more homogeneous in comparison with SB coatings and to have lower surface roughness. Contact angles confirmed the more hydrophobic nature of SB coatings. Potentiodynamic polarisation measurements and accelerated corrosion tests (exposure to acid vapours) revealed that protection efficiency not only increased with thickness but significantly depended on the coating structure. The structure of coatings depended on the rheological parameters of the formulations simulating their behaviour during storage, deposition, and formation of the dry coating. Combined electrochemical and vibrational spectroscopic experiments were used to simulate long-term outdoor exposure of the protective coatings. Ex situ IR RA spectroelectrochemical measurements showed that hydration was more prevalent with WB coatings, and oxidation of bronze at the interface eventually occurred (656 cm⁻¹ band). WB coatings with more free CO groups were more prone to degradation. In situ Raman spectroelectrochemistry confirmed the better protection efficiency of SB over WB coatings. The optical properties of the coatings on glass showed higher transmittance for WB coatings compared to SB coatings.
... However, in some cases an artificial protection of bronze objects is also desired. Traditionally, the most used commercial products for protection of bronze works include different waxes, such as Soter, acrylic resins, such as Incralac, and their combinations [5]. More recently, other possibilities attracted increased attention of researchers. ...
... More recently, other possibilities attracted increased attention of researchers. One of the most often studied anticorrosion solution envisage the use of organic protective films that formed on bronze surfaces during exposure to solutions of benzotriazole and its derivatives [5][6][7][8]. Such inhibiting layers are thin, i.e. about some tenths of nm [6]. ...
... Consequently, the promising application of sol-gel coatings is in protection of build materials [14]. Other examples of studied coatings for bronze are based on various polymers, ranging from conductive polymers [5], for which optical transparency is questionable, to fluoropolymers [5], acrylate/methacrylate [15] and polyurethanes [2]. ...
Two-component solvent-born polyurethane coatings for the protection of bronze from corrosion were prepared. Trisilanol-heptaisooctyl polyhedral oligomeric silsesquixane (POSS) nanoparticles were exploited to increase the coating protective efficiency. Its improvement was confirmed through a combination of characterisation techniques. In particular, the POSS addition caused an increase of the water contact angle, and an enhancement of the elastic connotation and abrasion resistance of the polyurethane coating. Potentiodynamic polarisation measurements also indicated that the coating containing POSS nanoparticles has an improved protection efficiency. Impedance spectroscopy revealed that the magnitude of low-frequency impedance of polyurethane coatings decreased more for the coating without POSS during exposure in electrolyte for thirty days. Ex situ IR reflection-absorption spectroelectrochemistry was exploited to get insight into the degradation of coatings during chronocoulometric charging at anodic potentials. IR reflection-absorption technique was also used to evaluate any possible effect of different stripper solutions on the bronze substrate.
... Bierwagen et al. [22] tested and developed a new protective coating for use on outdoor bronze monuments. Tests were performed on Incralac in different combinations of waxes and coatings based on hydrophobic fluoroorganic polymers. ...
... Research on the application of imidazole derivatives (including TMI) for copper protection in 0.5 M NaCl has shown that TMI is much more effective when dissolved in a chloride solution than when applied from an ethanol solution [24]. Bierwagen et al. [22] found that benzotriazole dissolved well in an alcohol solution, and that longer immersion of samples in prepared solutions provided better protection. But, taking into account the fact that large monuments cannot be immersed in solutions, it was found that brushing contact provides limited, though not equal protection. ...
... But, taking into account the fact that large monuments cannot be immersed in solutions, it was found that brushing contact provides limited, though not equal protection. It has been shown that BTAH does improve the electrochemical behaviour of bronze to some extent, but not to the expected level [22]. Rahmouni et al. [21] performed some preliminary studies on modern bronze, covered with an artificial patina. ...
Copper and high copper alloys tend to passivate in humid air. In clean humid air, cuprite slowly transforms to black tenorite. If atmosphere contains aggressive species, acid rain might effect the formation of different corrosion products. The patina that forms upon exposure to urban acid rain also depends of the composition of the base alloy. In the present study three different alloys were investigated: leaded bronze, usually used for sculptures, unleaded bronze as an alloy without an impact on the environment, and new type of bronze alloy, silicon bronze. The electrochemical measurements were performed to investigate the different bronze properties in simulated urban acid rain that contained carbonates, sulphates and nitrates, acidified to pH 5. Morphological characteristics of the three different bronzes were studied and SEM/EDX analysis of the corrosion products was performed. It was found that silicon bronze has higher corrosion resistivity than unleaded bronze, the former having higher corrosion resistivity than leaded bronze. In addition, time dependant electrochemical impedance spectroscopy measurements showed that polarization resistances for silicon bronze and unleaded increased with time, whereas it decreased for leaded bronze. The corrosion layer on silicon bronze is more compact and thinner due to homogeneous microstructure.
... Nowadays, protective coatings are often based on acrylic resins, fluoropolymers and waxes, containing or not containing corrosion inhibitors. In particular, Incralac ® (a solution of methyl-methacrylate/ethyl-methylacrylate copolymer, containing benzotriazole), Soter ® (a commercial product consisting of 20–24 wt% crystalline wax, BTA and synthetic organic polymer , dispersed in turpentine and ether), various microcrystalline waxes dispersed in white spirit or double-layer systems, such as Incralac ® + wax, have been widely used3456 . Fluoropolymers have also been used and tested as single coating systems or as topcoats because of their high resistance to degradation [6,7]. ...
... In particular, Incralac ® (a solution of methyl-methacrylate/ethyl-methylacrylate copolymer, containing benzotriazole), Soter ® (a commercial product consisting of 20–24 wt% crystalline wax, BTA and synthetic organic polymer , dispersed in turpentine and ether), various microcrystalline waxes dispersed in white spirit or double-layer systems, such as Incralac ® + wax, have been widely used3456 . Fluoropolymers have also been used and tested as single coating systems or as topcoats because of their high resistance to degradation [6,7]. Organosilane coatings attracted a significant research attention in recent years, due to their protective efficiency towards the corrosion of several alloys891011 . ...
... They are focused on 3-mercapto-propyl-trimethoxy-silane (PropS- SH)121314151617, 3-mercapto-propyl-triethoxy-silane [18] , octadecyl- trimethoxy-silane [19], glycidoxy-propyl-trimethoxy-silane [20], -aminopropyltriethoxysilane (-APS) [21] , or [triethoxy-silylpropyl]tetrasulfide [22]. However, only few papers consider the coating resistance to environmental stresses, like UV radiation, temperature or dry/wet cycles [6,7,12,14,15] , or investigate the corrosion resistance of silane coatings on pre-patinated surfaces [12,14,15,23]. In our previous works12131415 , 3-mercapto-propyl-trimethoxy- silane (PropS-SH) containing or not containing CeO 2 nanoparticles was tested as a protective coating for quaternary bronze (Cu-Sn- Zn-Pb) exposed to the outdoor atmosphere, within the frame of a research project devoted to the protection of outdoor bronze monuments. ...
3-Mercapto-propyl-trimethoxy-silane (PropS-SH) coatings, with or without the addition of three types of oxide particles (CeO2 (nano-sized), TiO2 (nano-sized) and La2O3 (micro-sized)), were applied on quaternary bronze (Cu-Sn-Zn-Pb) and tested through natural and artificial exposures. In particular, uncoated and coated samples were exposed both in the coastal town of Rimini (Italy) under sheltered/unsheltered conditions and in a climatic chamber where the samples underwent temperature/UV cycles, at constant humidity. The sample surfaces were periodically characterized by SEM, EDS, micro-Raman, FTIR and XRD techniques. Moreover, during natural exposures, runoff rainwater was collected monthly, in order to evaluate the release of the alloying metals from bronze by atomic absorption spectrometry (AAS). The results showed that micro-scale cracking and spalling phenomena took place during natural exposure, partly limiting the protective efficiency of the organosilane coating. In fact, UV radiation has a strong influence on coating performance, inducing structural modifications of the polymer. Oxide particle- and especially TiO2-charged coatings proved to be more resistant to UV degradation.
... Bierwagen et al. [22] tested and developed a new protective coating for use on outdoor bronze monuments. Tests were performed on Incralac in different combinations of waxes and coatings based on hydrophobic fluoroorganic polymers. ...
... Research on the application of imidazole derivatives (including TMI) for copper protection in 0.5 M NaCl has shown that TMI is much more effective when dissolved in a chloride solution than when applied from an ethanol solution [24]. Bierwagen et al. [22] found that benzotriazole dissolved well in an alcohol solution, and that longer immersion of samples in prepared solutions provided better protection. But, taking into account the fact that large monuments cannot be immersed in solutions, it was found that brushing contact provides limited, though not equal protection. ...
... But, taking into account the fact that large monuments cannot be immersed in solutions, it was found that brushing contact provides limited, though not equal protection. It has been shown that BTAH does improve the electrochemical behaviour of bronze to some extent, but not to the expected level [22]. Rahmouni et al. [21] performed some preliminary studies on modern bronze, covered with an artificial patina. ...
In humid atmospheres, copper and bronze passivate, with the formation of an oxidized layer (patina). Patinas may also be created by chemical patination procedures, which are frequently used to achieve special visual effects. However, unless these patinas are effectively protected, corrosion may be initiated when they are exposed to a polluted atmosphere. In the present study the stability of the green nitrate and the green chloride type of patinas, and of electrochemically formed patina, was investigated, as well as suitable protection methods. Two inhibitors, dissolved in different solutions, were used: benzotriazole and the less hazardous imidazole type of inhibitor, and waxes. The dissolving of untreated and pre-treated surfaces, in test solutions representing urban rain (pH 5.0), was investigated by means of potentiodynamic techniques. The microstructure of the patinas and the corrosion products was investigated by SEM/EDX. It was found that both investigated inhibitors inhibited the corrosion of electrochemically formed patina, and of the green chloride type of patina, but were ineffective in the case of the green nitrate type of patina. The difference between the performance of the investigated inhibitors when brushed onto patinated bronze, and when the bronze is immersed in a solution containing the dissolved inhibitor, was determined.
... For the final protection, the surface of bare or pre-patinated bronze artefacts may be brushed, sprayed or wiped with natural, synthetic or microcrystalline waxes that are sometimes doped with organic inhibitors, such as benzotriazole (BTAH) [10][11][12][13][14]. BTAH has now been used as an inhibitor for more than 50 years. ...
... For the final protection, the surface of bare or pre-patinated bronze artefacts may be brushed, sprayed or wiped with natural, synthetic or microcrystalline waxes that are sometimes doped with organic inhibitors, such as benzotriazole (BTAH) [10][11][12][13][14]. BTAH has now been used as an inhibitor for more than 50 years. It protects copper and copper alloys from both atmospheric and underwater corrosion in various fields of application [1,10,12,13]. Its use in the protection of different patinas on bronze is not well understood, though several studies have been conducted [10,11,15] and, of course, applied in the field by conservationists from the beginnings of BTAH use. ...
... It protects copper and copper alloys from both atmospheric and underwater corrosion in various fields of application [1,10,12,13]. Its use in the protection of different patinas on bronze is not well understood, though several studies have been conducted [10,11,15] and, of course, applied in the field by conservationists from the beginnings of BTAH use. Some new inhibitors have also been investigated [12,16]. ...
Copper and its high copper alloys (bronze) tend to passivate in humid air, forming an oxide layer (patina), which protects copper and its alloys from further corrosion processes. Sometimes there is a need to delay or stop further corrosion processes. In this case the surface is protected with natural, synthetic or microcrystalline waxes that are sometimes doped with organic inhibitors, such as benzotriazole. The aim of the present study was to test some organic compounds, including myristic acid and Paraloid B44, as a common finish for bronze sculptures. The mechanism of copper and bronze aging and its influents were determined in a test solution of urban rain.A classic electrochemical approach was used to study the corrosion behaviour of copper and its alloys. Untreated and pre-treated surfaces were investigated by means of different electrochemical techniques: potentiodynamic measurements, linear polarization measurements and electrochemical impedance spectroscopy. The properties and structure of the film formed were characterized by contact angle measurements and scanning electron microscopy (SEM).The possible use of myristic acid was evaluated as an alternative to the use of natural, synthetic or microcrystalline waxes for the protection of bronze artefacts.
... The first protective coating tested on archaeological metals was triazole and its derivatives. Triazoles have a long history in metallic protection because they were used as an inhibitor of copper corrosion in the industrial field [25][26][27]. The compounds are heterocyclic molecules with general chemical formula C2H3N3, having a five-membered ring of two carbon atoms and three nitrogen atoms ( Figure 2). ...
... Amongst different triazole-based compounds, the research highlighted the benzotriazole (BTA, C6H5N3) as it is the most efficient inhibitor at rather low concentration. BTA is diffusively applied in corrosion science, as reviewed by Finsgar and Milosev [26], and it is the most successful commercial inhibitor used also in conservation practice since the last decade. Amongst its advantages appreciated for archaeological metals, BTA counts its long-lasting life in a chloride-rich environment and its effectiveness in inhibiting hydrolysis of CuCl to Cu2(OH)3Cl, which is evaluated at 99% [27]. ...
In the last decades, the interest in the development of protective coatings for movable and immovable Cultural Heritage (CH) assets has decidedly increased. This has been mainly prompted by the raising consciousness on preservation requirements for cultural artefacts and monuments, which has consequently determined the development of new protective products. From acrylic resins used at the end of the last century to the up-to-date biomaterials and nanoparticles employed nowadays, the research has made a giant step forward. This article reviews the progresses, the technical challenges, and the most recent advances in protective coatings for archaeological metal, glass, and stone artefacts. It aims at offering a comprehensive and critical overview of the progressions in conservation science and displaying how research has optimized polymers in order to solve deterioration problems. Attention is given to recently developed materials, hybrid coatings, and corrosion inhibitors. This work seeks to provide a reference point for future research and to offer a wide-ranging introduction on the newly available material technologies to restorers and conservators.
... For the outdoor protection, the bet has been laid on various polymeric materials. Consequently, investigations of polyurethanes [7,8], methyl methacrylates [9], and fluoropolymers [10][11][12] could be found in the literature. Most of these studies were performed on patina-free bronze surfaces, although patina can form on the bronze surfaces under exposure to air [1], or can even be intentionally induced for protective and coloristic reasons by the artists themselves [13]. ...
... In the case of works of art exposed in outdoor environments, fluoropolymers stand out as a potential solution thanks to their weathering resistance. Firstly, coatings based on polyvinylidene difluoride (PVDF) building blocks (-CH 2 -CF 2 -) were examined on patina-free bronze surfaces [10], but the adhesion was not sufficient. Although PVDF fluoropolymers exhibit an outstanding durability, high temperature treatments are often required for their processing. ...
Two types of innovative coatings based on fluoroethylene/vinylether alternating copolymers are investigated as protective systems for bronze works-of-art. The influence of a polyhedral oligomeric silsesquioxane (POSS), i.e. open-cube trisilanol-heptaisooctyl-POSS, on the surface, mechanical, optical and electrochemical properties of coatings is examined. It is found that the isooctyl groups in the organic shell of POSS cause an increase in the hydrophobicity of the surface. On the other hand, nanoindentation tests show that the reduced modulus, hardness and plasticity index decrease with the addition of POSS, while abrasion resistance is slightly improved. Haze of coatings increases when POSS nanoparticles are present. More importantly, a beneficial effect of POSS addition on the protective efficiency against corrosion is assessed by exposure of coatings to acidic vapours and electrochemical treatments. In this regard, potentiodynamic polarisation clearly shows that the protective efficiency is systematically larger for coatings comprising POSS. The ex situ IR reflection-absorption spectroelectrochemistry shows that cuprous oxide can eventually form at the coating|bronze interface, which is identified through the spectroelectrochemistry of unprotected bronze.
... Incralac ® also contains benzotriazole (BTA) as a copper corrosion inhibitor and chelating agent (suspected of carcinogenicity [4]), together with a levelling agent (either Paraplex G-60, which is epoxidized soybean oil, or a silicone oil). BTA also acts as a coating UV stabilizer [5]. ...
... Following this approach, micro-crystalline wax and other organic polymers, such as poly-siloxanes, were later developed [5][6][7][8][9]. Among the others, 3-mercapto-propyl-trimethoxysilane (PropS-SH) proved to be effective for the protection of bare Cu and Cu-based alloys in NaCl solution [10][11][12][13], as well as in synthetic acid rain [14]. ...
A 3-mercapto-propyl-trimethoxysilane coating (PropS-SH) applied on Cu-Si-Mn bronze, patinated by “liver of sulphur”, was investigated as a non-toxic alternative to Incralac®, usually applied on outdoor artistic bronzes. Electrochemical testing was performed in synthetic acid rain. Exposure to temperature/UV cycles and ac- celerated corrosion test simulating unsheltered exposure to rainwater was also carried out. The exposed samples were characterised by FEG-SEM coupled with EDS on FIB cross-sections and XPS on free surfaces. The black patina without protective coating was scarcely protective against bronze corrosion and easily transformed into cuprous oxide. PropS-SH coating fully preserved the black patina microstructure and phase constituents (cuprous oxide and cuprous sulphide). The PropS-SH coating also resulted more protective than Incralac® when aged under run-off conditions. Selective dissolution of copper from the silicon bronze alloy was observed on both uncoated and Incralac®-coated bronze, leading to the formation of an internal Si-rich corrosion layer.
... Mineral phases detected by XRD on treated and untreated samples after weathering,[57].Despite these results, a relationship between the thickness of the Cu(I)BTA on bare bronze and the protectiveness leads the author to conclude that brush or spray applications only produce very thin films whose effect as physical barrier are negligible. Bierwagen et al.[58] also show the low efficiency of BTAH when it is applied as a pre-treatment on bronze after short immersion times. Better performances are obtained for longer immersion times (100 to 1000 minutes) and higher Kosec et al.[60] have studied the efficiency of three protective methods, among which BTAH, on bare and artificially patinated bronze. ...
Metallic heritage artefacts represent cultural traces of our past, and for this reason, their preservation and transmission to future generations is important. To protect copper-based artworks exposed outdoors, several conservation strategies are followed, including the use of organic corrosion inhibitors. Inhibitors are usually borrowed from the industrial field. However, the surface state of the metal with the presence of complex corrosion layers, and the protocol of inhibitors' application differ considerably from the industrial ones.The present study specifically addresses corrosion inhibitors for conservation of copper-based exposed artifacts by an innovative physico-chemical approach. The approach takes into account the complexity of the corrosion layer under investigation: a naturally corroded copper plate, representative for outdoor long-term corrosion have been chosen. For the study, three organic molecules, characterized by different chemical functions have been selected as test inhibitors: benzotriazole (BTAH), an azole compound, employed in conservation, which efficiency is debated and its use discouraged due to toxicity; decanoic acid (HC10) a long-chain fatty acid that has been proposed as treatment for heritage objects; benzotriazole-5-carboxylic acid (5CBT), a compound with mixed azole-carboxylic functions.The reactivity of the inhibitors with synthetic mineral phases representative of corrosion products as well as ancient corroded samples (100 years) before and after 6-months outdoor exposure have been investigated by combining observations at the nanoscale (TEM, FIB-tomography) to those obtained at the microscale (Raman, SEM-EDS) and global/bulk observations (colour, surface tension, XRD). Additional experiments in marked environment allowed to investigate changes in permeability (D₂O immersion) and the evolution of passive behavior (KBr immersion).Two reaction mechanisms have been observed and a relationship with the efficiency and durability of the inhibition is proposed. The molecules BTAH and 5CBT interaction with copper atoms occurs via the azole function and both molecules react according to an adsorption-precipitation mechanism forming an adsorbed amorphous complex (nanometric film) on the substrate mineral phase (cuprite and brochantite). The two treatments on the ancient corrosion layers differ for their depth of penetration, with Cu-BTAH complex formation being detected until the cuprite inner layer, while 5CBT complexation is observed only in the outer part of the brochantite. This has an impact on the water permeability and passivity, with the BTAH treatments showing the best results, and suggests a complex formation with the outer cuprite layer in this last treatment. The carboxylic function in HC10 leads to the precipitation of copper decanoate by a dissolution-precipitation mechanism. Crystals of decanoate are formed on the outer surface of brochantite: this confers near super-hydrophobicity to the sample after treatment. However, the lack of bond between the precipitate and the surface determines the loss of the surface-deposited hydrophobic layer after 6 months of outdoor exposure.In addition to these phenomenological results, a new methodology based on the KBr experiment for testing inhibitors for copper corroded artefacts is also proposed.
... Microcrystalline wax Bronze (Letardi 2000, Joseph et al . 2007 TWA_2095(*) Microcrystalline wax Bronze, Bronze + artificial patinas (Price et al. 1995, Otieno-Alego et al. 1998 Soter_201 LC Microcrystalline waxes with BTA Bronze (Letardi et al. 1998, Letardi 2000 Renaissance wax Cosmolloid 80 and BASF-A waxes Bronze, steel, precorroded steel (Argyropoulos et al. 2007, Swartz and Clare 2015 Wax (Bierwagen, Shedlosky, and Ellingson 2003, Ćurković et al. 2010, Kosec, Legat, and Miloev 2010, Hosbein, Swartz, and Clare 2014, Ramírez Barat and Cano 2015 Paraloid of the development of more refined field measurement setups and in laboratory application to characterize patinas and protective treatments. The lack of generally accepted standards often makes the comparison of results from different studies far from straightforward. ...
Electrochemical impedance spectroscopy (EIS) is a technique widely used in the field of corrosion science and for coatings evaluation. Its application to the field of cultural heritage started in the early 1990s. Since then, around a hundred references have
appeared in conservation and scientific literature addressing different topics such as corrosion processes, field measurements, conservation assessment, and protective coatings evaluation. All of these research results constitute highly valuable information for metal conservators. This paper addresses the state of the art on available setups for EIS measurements in heritage science and presents an overview of the results on different coatings and substrates.
... The corrosion protection of an organic coating depends largely on the intrinsic barrier properties of the polymeric film towards oxygen, water, and aggressive species, but can be reinforced by entrapped corrosion inhibitors [1][2][3]. In the case of bronze artworks exposed outdoors, commercial coatings such as Incralac ® and Soter ® contain benzotriazole (BTA) that operates in the dual functions of an inhibitor of bronze corrosion and an anti-UV additive [4]. In these coatings, the inhibitor dissolves in the electrolyte (in the rain) and penetrates through the coating, so producing an inhibited solution that exerts a protective action at the coating/metal interface. ...
The corrosion protection of coatings can be reinforced by the addition of entrapped corrosion inhibitors. β-cyclodextrin (β-CD) can form inclusion complexes with small inhibiting organic molecules that, when entrapped in coatings, allow the inhibitor release and adsorption at corrosion initiation sites. In this paper, several Nuclear Magnetic Resonance (NMR)-based experiments (e.g., Complexation-Induced Shifts (CIS), NMR titration, Diffusion-Ordered Spectroscopy (DOSY)) were performed to study the stability and geometry of a complex formed by β-cyclodextrin with 5-mercapto-1-phenyl-tetrazole (MPT). The complex was also detected by Electrospray Ionization (ESI) mass spectrometry and characterized by Fourier Transform Infrared (FTIR) spectra. Its influence on the protectiveness of a silane coating against bronze corrosion was evaluated in plain (AR) and concentrated (ARX10) synthetic acid rain, under different exposure conditions. In particular, the time evolution of the polarization resistance values during 20 days in ARX10 and the polarization curves recorded at the end of the immersions evidenced a higher protectiveness of the coating with the β-CD–MPT complex in comparison to that containing only MPT or only β-CD. The cyclic AR spray test carried out on coated bronze coupons with cross-cut scratches evidenced the absence of underfilm corrosion starting from the scratches only in the complex-containing coating.
... To obtain a specific shade, the bronze surface can be treated with different chemical solutions, such as chlorides, nitrates and sulphates. Wax, lacquer, or varnish were applied to saturate the surface color and protect the patina and the metal surface from corrosion [4][5][6]. Among these different materials, natural wax -such as beeswax -is one of the mostly used coating for indoor bronzes, thanks to its properties such as low water vapor permeability and low gloss [7]. ...
In this research, we propose an advanced system for the cleaning of wax-based coatings applied on indoor bronzes. To this aim we developed a new kind of eco-friendly gel based on PHB (poly-3-hydroxybutyrate) used as thickening agent, biodiesel (BD) and dimethyl carbonate (DMC). BD is a mixture of methyl esters obtained from palm oil, which acts as cleaning agent while DMC was added as additional solvent to partially solubilize PHB and forming a gelly phase. For the first time a PHB-based gel obtained by mixing two solvents with different proprieties was proposed, expanding the range of possible formulations, that can be used according to the specific restoration purpose. After the preliminary characterization of chemical and physical properties of the gel, an ad hoc analytical protocol was implemented to evaluate both the cleaning efficiency and the release of residues on the treated surfaces. Standard samples were prepared following ancient recipes and submitted to spectroscopic and chromatographic analysis before and after the cleaning procedures. Finally, the performances of PHB-DMC/BD gel were assessed on a real case of study presenting a wax-based coating: the Pulpito della passione attributed to Donatello and dated back to 1460. In situ analysis demonstrated the high cleaning efficiency of the proposed systems also for the removal of aged coatings.
... The use of electrochemical impedance spectroscopy (EIS) for the evaluation of patinas and coatings in the field of cultural heritage has raised some interest in the latest decades. Traditional coatings usually applied by conservators such as acrylic resins and waxes have been evaluated using this technique, which has also been used for testing in the development of new coatings and inhibitors [1][2][3][4][5][6][7][8]. Besides these studies, researchers have also worked in the development of portable systems to carry out EIS measurements directly on sculptures and monuments [9][10][11][12]. ...
Electrochemical impedance spectroscopy (EIS) is widely used in corrosion studies and coatings evaluation for metals. However, its applicability to conservation problems in the field cultural heritage is limited by the practical difficulties of performing in-situ measurements on sculptures and monuments. Authors have proposed use of a gel polymer electrolyte (GP-E) cell as an electrochemical sensor to overcome the difficulties of handling liquid electrolytes on irregular surfaces. The aim of this paper is to optimize the design of the G-PE cell for in-situ EIS measurements on metallic cultural heritage, and to characterize in detail the possible effects of the configuration of the cell on the EIS spectra. Parasitic impedances from the reference electrodes have been analyzed to discriminate the response of the working electrode from that arising from artifacts from the cell setup, in order to be able to make an accurate interpretation of the results. This has allowed optimizing the different parameters and designing an effective tool for conservation assessment in metallic cultural heritage.
... The inhibition and structure of BTA on copper alloy has been mostly studied using immersion treatment in hot, dilute solution [25,26] or impregnation under vacuum [27]. However, BTA is often incorporated into coating formulations as an anti-corrosion additive and for its UV absorption properties [28,29]. For example, Incralac is an acrylic coating made up of Paraloid™ B44, benzotriazole, a carrier solvent and levelling agent [30]. ...
Copper can have a beneficial or unfavorable effect on coating performance, depending on the additives present in the formulation. The distribution of copper was studied in acrylic coating formulations on brass substrates with and without benzotriazole to gain insights into the role of copper ions. Using depth profiling secondary ion mass spectrometry it was found that on ageing copper migrated from the coating towards the substrate in the presence of benzotriazole, possibly due to inhibition at the coating-metal interface. However, closer inspection by ToF-SIMS shows an even distribution of BTA in the coating and no evidence of inhibition via complexation or chemisorption on the metal surface.
... Since the mid 90s conservation scientists have started to use this technique in the evaluation of protective coatings for metallic cultural heritage [7][8][9][10][11], and in the last three decades several researchers have been working in the development of specific methodologies and portable devices to its application in the in situ evaluation of patina and coatings on outdoor sculpture and monuments [12][13][14][15][16][17][18]. Concurrently with the restoration process of the sphinxes and within the framework of CREMEL project (Conservation-REstoration of Metal cultural heritage with ELectrochemical techniques) authors have been working in an agar gel-polymer electrolyte (G-PE) cell specifically designed for in situ measurements on cultural heritage overcoming some of the limitations of previous designs [19,20]. ...
In any conservation project, conservators have to address several questions to design the appropriate intervention strategy. Among them, the effectiveness and duration of protective treatments is an important issue, not easy to evaluate. In the field of metallic cultural heritage, electrochemical techniques such as electrochemical impedance spectroscopy (EIS) can be used to evaluate patinas and protective coatings performance. Widely used in industrial applications, the use of these techniques in conservation science is much more recent and limited.
... A further point was the preference for a safe product. In recent years, several studies have been carried out to individuate or develop new successful coatings for metals conservation [4,5,6]. However, only a small range of polymers is still used in common practice. ...
... Environmental adverse effects of acid rain include changes in the leaching rates of nutrients from plant foliage and soil nutrients, acidification of lakes and rivers, effects on metabolism of organisms and corrosion of structures [10] [11]. In addition to that, acid rain is also responsible for reduction of visibility and deterioration of historical structures especially by damaging the details on historic places or sculptures [5] [12]. Precipitation composition thus is an indispensable measurement and helps to understand the comparative importance of the different sources of these materials. ...
The urban centers of developing countries like Karachi city in Pakistan are facing the menace of air pollution and at-mospheric wet deposition can be used as a tool for monitoring the quality of air. In this study, rainwater samples from eighteen different towns of Karachi were collected during monsoon season (July to September, 2013) in triplicate and analyzed. Their pH (range 6.2-7.9), electrical conductivity (range 0.02-0.21 m.S/cm), total dissolved solids (range 32-159 mg/l), dissolved oxygen (range 6.3-8.2 mg/l) and hardness (23-89 mg/l) were immediately monitored within next twenty four hours of sample collections. The samples were than acidified and analyzed for the presence of major cations ammonium, sodium, potassium, magnesium and calcium by flame atomic absorption spectroscopy and flame emission spectroscopy. The anions fluoride, chloride, nitrate, carbonate and sulphate were analyzed by ion chromatog-raphy. The results of the analysis were compared with the values provided by WHO guidelines in order to access the quality of water. Most of the rainwater samples were completely free from considerable pollution and meet the WHO standard values. However, in Lyari, Gulshan, Shah Faisal, Landhi, Malir and Gadap town the concentration of Mg+2 and in North Nazimabad, Korangi, Gulshan, Saddar, Lyari, SITE and Keamari town the concentration of NO3- are above the WHO standards, indicating their presence from air pollution.
... The PVDF/acrylic blend increases adhesion to an average range. [52][53][54][55][56][57] However, a more usual approach is the introduction of fluorine into the backbone or side chain of silicon-based or acrylic-based polymers to prepare a polymer with properties of both fluoropolymers and silicon or acrylic polymers. 7,26,44,46,47 Brugnara et al. 9 reported that fluorinated polymers show hydrophobicity significantly higher than the usual acrylic polymers. ...
The conservation and protection of historic monuments or culturally significant structures have recently attracted much attention from material scientists. This review is given of the various aspects of the monuments protection such as the main reasons of damaging and spoiling of the historical monuments, the factor of contact angle as one of the essential parameters in the selection of polymeric coatings, and some of usual types of polymeric materials used for monument protection. There has been growing interest in developing novel materials for using in protective fields. Nowadays, the polymeric coatings, especially those with high hydrophobicity, are widely used to decrease or even stop further deterioration of historical monument. This review presents some of the most well-known polymers used as protective materials such as acrylics, alkoxysilanes, fluorinated polymers, and hybrid organic–inorganic coatings. Furthermore, hybrid organic–inorganic coatings as a new class of materials are increasingly interesting materials because of their extraordinary properties deriving from the combination of the different building blocks and it is attempted to focus on this materials.
... However, to the best of our knowledge, the quantitative study of patina-covered bronze is scarcely reported in the literature [36]. Certain authors announce the importance of the patina layer to the electrochemical properties of the bronze electrode, but no comparative study is reported in their articles [37,38]. ...
Bronze statues exposed to an urban area suffer corrosion processes induced by acid rainwater. Use of corrosion inhibitors is one of the most convenient and cost-effective techniques to mitigate it. In a previous work, it was found that 4-methyl-1-p-tolylimidazole (MTI) is non-toxic and efficient inhibitor of copper, and thus we will examine the anticorrosive effect of this substance to copper-tin bronze. First, with bare Cu–6Sn (wt%) bronze, inhibiting efficiency in artificial acid rainwater in urban environment was evaluated by Tafel extrapolation, polarization resistance, and electrochemical impedance spectroscopy (EIS) methods. This study showed that all three methods supply similar inhibiting efficiency validating thus the use of EIS, the least invasive method. This study was followed by the evaluation of inhibiting effect on patinated bronze in sulphate medium. A quntitative study about the inhibiting effect on patinated bronze is scarcely reported in the literature. EIS data revealed three capacitive loops. Comparison with EIS obtained in bare specimens allowed attributing the additional capacitive loop located at the highest frequency domain to the dielectric property of the patina layer. The impedance modulus determined in presence of MTI increased markedly with immersion time, revealing a protective effect of this non-toxic corrosion inhibitor.
... Environmental adverse effects of acid rain include changes in the leaching rates of nutrients from plant foliage and soil nutrients, acidification of lakes and rivers, effects on metabolism of organisms and corrosion of structures (Kelly et al., 1989;Bard, 1999). In addition to that, acid rain is also responsible for reduction of visibility and deterioration of historical structures especially by damaging the details on historic places or sculptures (Elsom, 1987;Bierwagen et al., 2003). Man is also primarily responsible for the enrichment of many trace elements now found in the atmosphere caused by the combustion of fossil fuels, including such additives as the lead in gasoline, roasting of ores for refining metals, processing of crustal materials for manufacturing cements, and burning of waste materials (Baubel et al., 1994). ...
In the present study, the precipitation near Büyükçekmece Lake, which is one of the important drinking water sources of Istanbul city, was studied during October 2001–July 2002. Seventy-nine bulk precipitation samples were collected at two sampling stations near the Lake (41°2′35″N, 28°35′25″E and 41°5′30″N, 28°37′7″E). The study comprised the determination of H+, Cl−, NO3−, SO42−, NH4+, Na, K, Mg, Ca, Al, Ba, Fe, Cu and Mn concentrations in bulk deposition rain event samples. The average volume-weighted pH value was found to be 4.81, which points out that the rain is slightly acidic. High sulfate concentrations were observed together with high H+ ion values. Sulfur emissions were the major cause for the observed high hydrogen ion levels. On the basis of factor analysis and correlation matrix analysis, it has been found that in this region, acid neutralization is brought about by calcium rather than the ammonium ion. The varimax rotated factor analysis grouped the variables into four factors, which are crustal, marine and two anthropogenic sources.
This research presents the modification of ZnO nanoparticles by Glycidoxypropyltrimethoxysilane (GPTMS) to produce hybrid nanostructured additives to improve the weathering resistance of epoxy silicone coatings. The modified ZnO nanoparticles were incorporated into epoxy silicone coatings at different loading dosages. The coatings were then weathered in an accelerated weathering chamber and removed after specific intervals (0, 500, and 1000 h) for further characterization. The effect of different loadings of modified ZnO nanoparticles (0.1, 0.5, and 1 wt%) on the weathering resistance of epoxy silicone coatings was studied using SEM, AFM, FTIR, and contact angle measurement, UV–visible spectroscopy, optical microscope, gloss, Vickers hardness, and gonio-spectrophotometer. All results showed that the addition of modified nanoparticles effectively promoted (6 times improvement based on carbonyl index) the weathering resistance of the epoxy silicone coating. It was also concluded that the coatings filled at a low level (0.1 wt%) of GPTMS-modified ZnO provided much more superior weathering performance than those loaded with higher filler content (0.5 and 1 wt%). It was explained by the more crosslinked network formed and the fine distribution of modified filler within the matrix at low filler content.
When bronze or artificially patinated bronze is exposed to an outdoor environment that contains aggressive ions such as sulphates, nitrates, and carbonates, the surface of the bronze changes its appearance due to the formation of corrosion products on the surface. Research is being conducted on versatile protective measures that can be used to protect the surface from these changes. A recently synthesised fluoropolymer-based coating with mercaptopropyl groups, i.e. a 3-component fluoropolymer coating FA-MS-SH (silane-modified poly methylmethacrylate (MS) with added mercaptopropyltrimethoxy silane (SH) and a fluoroacrylate (FA)) was explored in detail in this work where its protective mechanism on sulphide patinated bronze was investigated. Electrochemical tests were conducted on the sulphide patinated bronze with and without the 3-component coating FA-MS-SH. Furthermore, FA, MS and SH alone and various combinations and concentrations of FA-MS were studied in order to determine the protective effect and properties of each component. Colour change and contact angle measurements were also defined. FIB-SEM measurements and GCIB-XPS depth profiles were carried out to study surface bonding with the sulphide patina in detail.
A mechanism for the protection of sulphide patinated bronze was presented through the use of a multi-analytical tool approach. It was shown that FA physisorbed on the patinated surface, while MS and blends of the components chemisorbed on the layer of sulphide patinated bronze, also resulting in the surface being efficiently protected from corrosion processes.
The creation of innovative tools, objects and artifacts that introduce abstract ideas in the real world is a necessary step for the evolution process and characterize the creative capacity of civilization. Sculpture is based on the available technology for its creation process and is strongly related to the level of technological sophistication of each era. This paper analyzes the evolution of basic sculpture techniques (carving, lost-wax casting and 3D scanning/printing), and their importance as a culture footprint. It also presents and evaluates the added creative capacities of each technological step and the different methods of 3D scanning/printing concerning sculpture. It is also an attempt to define the term "material poetics", which is connected to sculpture artifacts. We conclude that 3D scanning/printing is an important sign of civilization, although artifacts lose a part of material poetics with additive manufacturing. Subsequently, there are various causes of the destruction of sculptures, leaving a hole in the history of art. Finally, this paper showcases the importance of 3D scanning/printing in salvaging cultural heritage, as it has radically altered the way we "backup" objects.
Bronze surfaces, whether bare or patinated, tend to change when exposed to an outdoor atmosphere. Art made of bronze which is exposed to the outdoors is usually artificially patinated. This patina changes when exposed to rain, especially in polluted rain, where sulphuric, nitric or carbonic acids are present.
In order to gain optimal protection of different patinas and consequently reduce the patina changes over the time different protection systems were developed, tested and tailored. Three types of patina (brown, green sulphate, and green persulphate) were prepared, protected and subsequently studied. The protections were based on two coatings (i) fluoropolymer based coating (FA-MS) and (ii) newly developed fluoropolymer based coating with addition of mercaptopropyl groups, named as alternative fluoropolymer coating (FA-MS-SH). Both the pure patinas applied on bronze surfaces as well as the bare bronze were electrochemically tested, first unprotected and then following the application of two different types of protection. After the protection was applied to the patinas, the change in colour was defined. Different techniques were utilised in order to define the morphology and structure of the patinas, as well as the change in colour following application of the coating. It was shown that a fluoropolymer coating (FA-MS) provided the most efficient protection to bare bronze and the sulphate patina, while a newly proposed alternative fluoropolymer coating (FA-MS-SH) offered good protection to bare and brown patinated bronze. A mechanism for the protection of bare and patinated bronze was suggested.
In the present work, the efficiency and time-degradation of new protective organic coatings for artificially patinated bronze based on nitrocellulose lacquer containing thiadiazole derivatives (2-mercapto-5-amino-1,3,4-thiadiazole and 2-mercapto-5-methyl-1,3,4-thiadiazole) as corrosion inhibitors were investigated. The samples were intermittently exposed to a solution simulating an urban rain (pH 5) and their behaviour was monitored for nearly three months by electrochemical impedance spectroscopy (EIS) measurements.
Optical microscopy examination of cross sections of bronze samples covered with patina and nitrocellulose lacquer, without and with inhibitors, was used to determine the thickness of the coatings. Fourier transformed infrared spectroscopy (FT-IR) was employed to put on evidence the chemical interactions between the organic inhibitors and nitrocellulose lacquer functional groups.
The best results were achieved in the presence of 2-mercapto-5-amino-1,3,4-thiadiazole into the nitrocellulose lacquer coating, which offers the highest long-lasting protection to patinated bronzes, without changing the visual appearance of the bronze surfaces covered with patina. This approach proved to be a promising alternative to benzotriazole in the development of highly protective coatings for patinated bronzes.
Electrical properties of thin dielectric films at the solid-liquid phase boundary are an important performance characteristic of many devices, coatings and sensors. In this paper, co-polymeric hydrogels of polyacrylic acid co-sulfonic acid, swollen with a salt solution to act as the solid electrolyte, were used to assess interfaces using electrochemical impedance spectroscopy (EIS) in a co-planar geometry. Silane-modified glasses were characterized by the co-planar hydrogel EIS cell and found to be distinguishable based on their surface monolayer chemistry. EIS measurements were also made on primed and painted metal substrates, using both test panels and an outdoor sculpture, Tony Smith's Stinger. The panels were then exposed to accelerated and outdoor weathering and showed degradation on the surface paint layers, which was observable electrochemically using EIS and confirmed visually by SEM. Electrochemical spectral features were compared between data from a standard paint-test cell versus this co-planar hydrogel cell; both cell types were able to measure coating capacitance, providing useful information about the condition of the bulk coating. Yet, sheet resistance (Rs) was a spectral feature seen only by the co-planar hydrogel cell. Thus, it can be concluded that the use of such co-planar hydrogel cells can provide an earlier warning sign to coating degradation and such cells provide a new type of spectral information that is not assessable by the standard geometry.
Preventive conservation is one of the most important processes used for saving artifacts. The corrosion inhibitors and protective coatings are highly recommended for protecting metals from degradation and corrosion process.
This research focuses on laboratory tests of five corrosion inhibitors and protective coatings on Bronze samples in order to measure the efficiency of these materials to be applied on Bronze artifacts. Two derivatives of acrylics, (Paraloid B72 and B82), two Amino acids (Cysteine and Valine), and Benzoteriazol (BTA) with concentration 3% were compared as a protective coating. Two laboratory assessment methods are used, weight loss and polarization tests. Bronze samples are divided into six groups, the first group is a blank group and the others apply one material for each group and each group contains three samples.
The tested samples are exposed to 1M copper chloride solution for 24 hours and measures are record. After this step we apply the materials on samples and expose these samples to temperature 40ᵒ and humidity 100% for 24 hours in a controlled chamber.
Weight loss test proved that the best Protection and inhibition efficiency of Martials is Cysteine efficiency record 99.71%. Paraloid B72 efficiency is 99.42% compared to other materials.
The electrochemical test illustrated that the best protection efficiency of these Martials are Paraloid B82 which is 99.74% and Paraloid B72 which is 99.64 %.
Key words: Bronze, protective coating, BTA, Amino acids, Polarization.
Poly(acrylonitrile-butadiene-styrene) (ABS) composites containing (i) hindered amine light stabilizer (HALS);(ii) nano-scale rutile titanium dioxide ( n-TiO2) ; and (iii) both HALS and n-TiO2 were prepared by melt-blending process. To prevent agglomeration of nanoparticles, the surface of the ra-TiO2 nanoparticles were modified to ensure a good dispersion. The pure ABS and ABS composite samples were under accelerated aging test for 28 days with a laboratory xenon arc lamp ( GB/T16422. 2-1999), and their ageing resistant properties were investigated by Izod unnotched impact, Izod notched impact properties measurements and fracture surface analysis. The morphologies of the unnotched impact fractured surface of pure ABS and ABS composites samples at different irradiation time were characterized by scanning electron microscope (SEM) and optical microscope. According to the SEM photos of brittle fracture (liquid nitrogen immersion) and impact fracture,it can be seen that cavities and knobs on fracture surface were formed by rupture of rubber phases dispersed in ABS when it was under lateral impact. On the other hand,the n-TiO2 less than 100 nm dispersed uniformly in ABS with no evident large agglomerated particles was helpful to its function as ultraviolet screen agents. With the UV shielding capability of nano-scale rutile TiO2 and HALS, the ageing resistance of ABS samples was improved. Moreover, the ageing resistance of ABS/ra-TiO2/HALS composites samples is better than that of ABS/rc-TiO2 and ABS/HALS composites samples, suggesting a synergistic effect between HALS and n-TiO2. After 28 days exposure to xenon arc lamp the retained percentage of Izod unnotched impact strength of ABS/2.0 wt% n-TiO2/0.6 wt% HALS composites samples was 47.9%, which was more than 2.5 times as high as that of pure ABS. At the same time the retained percentage of unnotched impact strength of ABS/0.6 wt% HALS composites samples was 29.2% after 28 days exposure to xenon arc lamp,which is attributed to diffusio n-controlled oxidation. The retained percentage of Izod unnotched impact strength of ABS/0.5 wt% n-TiO2 composites was only 23.8% after 28 days exposure to xenon arc lamp.The presence of n-TiO2 could confine degradation in a thin region close to the exposed surface. It is obvious that n-TiO2 could not only shield theultraviolet irradiated on ABS but also prevent impurity and HALS in ABS from being destroyed by ultraviolet. ABS/0.5 wt% re-TiO2/HALS composite samples had a higher unnotched impact strength, which was increased by 15.3% compared to pure ABS samples, and the tougheness of ABS was increased to a great extent. By impact fracture surface morphology analysis it was found that for unstabilized ABS specimens, there was a bigger smooth zone on fracture surface with very little impact strength retained only after four days laboratory weathering exposures. There is a correlative relation between proportion of smooth zone and retained percentage of unnotched impact strength of pure ABS samples after accelerated aging. The whole unnotched impact fractures surface of exposed and unexposed ABS/2.0 wt% n-TiO2/0.6 wt% HALS composites were white or gray,just as unnotched impact section of unexposed pure ABS, and there were few rubber particles and cavitation left by the pull-off of them exposed on the section.
Bronzes have been widely used to produce sculptures and other objects of art. Very often they are exposed to corrosive action of polluted atmosphere. Acid rain that forms due to the presence of polluting gases may cause extensive damage on the bronze objects. The SO 2 is one of the main pollutants in urban atmosphere due to the industrial activity and the emission by automotive vehicles. For this reason studies of bronze corrosion were performed in simulated acid rain with the composition: 0.2 g L -1 Na 2SO 4 + 0.2 g L -1 NaHCO 3 at pH 3. In order to preserve metal works from the aggressive atmosphere, organic inhibitors are often required. Previous investigations have shown that imidazole derivatives are good copper corrosion inhibitors in different media. In this work the efficiency of two imidazole based corrosion inhibitors: (4-methyl-1-(ptolyl) imidazole and benzimidazole), was examined on the Cu-6Sn bronze. Corrosion studies were performed by the potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The results have shown that both studied corrosion inhibitors efficiently protect Cu-6Sn bronze in sulphate-carbonate media.
Copper and copper alloys (bronze and brass) are usually employed in the manufacturing of cultural objects. When these alloys are exposed to the atmosphere, damaging corrosion products may form on their surfaces. Corrosion inhibitors are used to minimize the corrosion processes. However, the conditions that obtain the best anticorrosive performance of these inhibitors require the control of several chemical and operational parameters, which are, in practice, often chosen empirically. An experimental design was employed to determine the best values with respect to the concentration of 2-amino-5-mercapto-1,3,4-thiadiazole (AMT), the ethanol content and the immersion time of bronze in the AMT solution to achieve the most protective films on the bronze surface. Electrochemical impedance spectroscopy assays of bronze samples with and without previous immersion in the inhibitor solution and exposed to artificial rainwater were performed at the open circuit potential. The parameters and the influence of their interactions on the inhibitory effect of the film formed on the bronze surface were shown to be statistically significant. The conditions for achieving the most protective films were 0.060 M AMT, 90% v/v EtOH, and 90 min of immersion. (c) 2013 Published by Elsevier B.V.
A new coating system for archeological bronze protection that consists of a primer coating and a top coating was prepared in this study. The primer coating was prepared by mixing water-based acrylic emulsion with 1,2,3-benzotriazole, and the ultraviolet (UV) light-resistant top coating was prepared by mixing water-based acrylic emulsion with nano-sized TiO2 and SiO2 particles. UV light resistance and visible light transmission, contact angle, corrosion resistance, and mechanical properties of the new coating system were investigated and the results showed that UV resistance, hydrophobicity, oleophobicity, glossiness, and corrosion resistance all were improved. Application of the new system on real archaeological bronzes showed that the coating film was colorless, odorless, transparent, soft low-lustre, removable, and the original appearance of the archaeological bronze was well maintained.
Protection of surfaces directly exposed to the detrimental action of degradative agents (i.e. oxygen, air pollutants and bacteria) is one of the most important challenges in the field of conservation of works of art. Metallic objects are subjected to specific surface corrosion phenomena that, over the years, make mandatory the research of innovative materials that should avoid the direct contact between the metal surface and the weathering agents. In this paper, the set-up, characterisation and application of a new reversible material for preserving metal artefacts are reported. Micro-layers constituted of low-adhesive polystyrene (PS) films obtained from recycling waste packaging materials made of expanded PS were studied. The morphology and thickness of PS films were characterised by optical, atomic force and scanning electron microscopy (SEM). A further check on thickness was carried out by means of visible spectrophotometry doping the films with a hydrophobic dye. Thermal properties of the PS micro-layers were studied by means of differential scanning calorimetry coupled with optical microscopy. Permeability of the PS films to water vapour was also determined. The potential of the low-adhesive PS films, that enabled an easy removal in case of film deterioration, for preventing metal oxidation was investigated on brass specimens by simulating standard artificial corrosion programmes. Morphological and chemical (coupling the energy-dispersive X-rays spectrometry to SEM measurements) analyses carried out on these metal samples showed promising results in terms of surface protection against corrosion.
Electrochemical impedance spectroscopy (EIS) and SEM-EDX observations were used to evaluate the inhibiting effect of four thiadiazole derivatives, i.e. 2-mercapto-5-amino-1,3,4-thiadiazole (MAT), 2-mercapto-5-methyl-1,3,4-thiadiazole (MMeT), 2-mercapto-5-acetylamino-1,3,4-thiadiazole (MAcAT) and 2-mercapto-5-phenylamino-1,3,4-thiadiazole(MPhAT) on the corrosion of naked and artificially patinated bronze surface exposed to an acidic solution (pH 3) that simulates a strongly polluted rainfall. For comparison reasons, the inhibiting effect of benzotriazole (BTA) was also examined. In an attempt to better understand the influence of solution pH on the adsorption of the thiadiazole derivatives and to correlate their structural and electronic characteristics with the experimental inhibition efficiencies, quantum chemical calculations were performed starting with thiadiazole and its protonated derivatives. Finally, a possible inhibition mechanism of the thiadiazole protonated species on bronze corrosion was proposed. It was concluded that MMeT and MAT allow the stabilization of the patina layer, leading to the protection of the bronze substrate and their effectiveness significantly increase with the immersion time.
Bronze surfaces, as well as prepatinated surfaces on bronze, undergo chemical and visual changes when exposed to humid and polluted environments. For this reason, it is important to study the effectiveness of corrosion inhibitors on patinated-bronze surfaces. The aim of this study was to investigate different protection systems for patinated bronze, which are based on the use of two azole type inhibitors: 2-mercaptobenzimidazole and benzotriazole. The results of our practice confirmed that these inhibitors were very effective when immersed in a corrosive solution containing inhibitor for 24 h. The inhibited layers were then protected by a water-repellant layer. In the case of the studied patinas, green chloride and green nitrate patinas, applied over the brown artist's patina, were tested, as well as brown patina and the patina that develops on bare bronze. The study was performed after each chemical patination and the application of the two different inhibitors.The inhibition systems used on the different chemically achieved patinas were characterized by Raman spectroscopy and electrochemical techniques. The results of the Raman studies showed a chemical interaction of both inhibitors with copper and bronze but a versatile interaction between the inhibitors and the different patinas. The chemical interaction of benzotriazole was observed on the nitrate patina, whereas the mercaptobenzimidazole showed interaction also with the chloride-type patina. Electrochemical tests proved the interaction, which had been detected by Raman spectroscopy. Copyright © 2014 John Wiley & Sons, Ltd.
This work presents the application of voltammetry of microparticles (VMP) to the characterization of metallic artefacts. The paper illustrates the principle of the technique and the methods for the identification of metals and copper minerals. VMP can be considered a non-invasive technique as it requires a minimum amount of material for performing the analyses. To emphasize the efficacy of this technique regarding characterization of cultural heritage materials, two bronze artefacts of different historical periods were investigated. By using a paraffin-impregnated graphite electrode, the composition of the alloy and the copper minerals present in their patinas were analysed and identified. The results obtained from the electrochemical characterization were confirmed by complementary analysis carried out with X-ray fluorescence and X-ray diffraction.
The patina that covers bronze often has an aesthetic and/or historical value. It should therefore be protected from corrosion in aggressive urban environments. In the present study, two green chemically obtained bronze patinas were examined, as well as an electrochemical patina that resembles the natural patina. Different protective systems were applied to the samples: azole-based inhibitors in an ethanol solution, azole-based inhibitors in polymer coating or wax coating. The efficiency of these protective systems during immersion in simulated urban rainwater was monitored by electrochemical impedance spectroscopy. The results showed that the protection of patinated bronzes by the inhibitor/ethanol system was long-lasting and most effective for electrochemically patinated bronze. Protective properties of investigated inhibitor/Paraloid B44 systems were found to depend on inhibitor present in the coating as well as on properties of the patina layer on which it was applied. For all types of patina BTA/Paraloid B44 coating exhibited better protecting properties than MTI/Paraloid B44 coating. Carnauba wax was found to provide stabile and effective protection, especially for nitrate patinated bronze.
Various organosilane-treated SiO2 nanoparticles were dispersed in a 2-pack polyurethane coating. The influence of surface modification and silica content on the electrochemical behaviour of the resultant nanocoatings was investigated. Electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) variations were examined. The surface chemistry of nanoparticles and its effect on the resultant nanocoating morphology were also studied utilising FTIR, and TEM analyses. The results reveal that the presence of more hydrophobic groups and longer-lengthed hydrophobic chains on the surface of nanoparticles, greatly improves the interfacial interactions at the polymer/filler interfaces resulting in a better corrosion performance.
Acid deposition, more commonly known as acid rain, occurs when emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) react in the atmosphere (with water, oxygen, and oxidants) to form various acidic compounds. These acidic compounds then fall to earth in either a wet form (rain, snow, and fog) or a dry form (gases, aerosols, and particles). Prevailing winds transport the acidic compounds hundreds of miles, often across state and national borders. At certain levels the acidic compounds, including small particles such as sulfates and nitrates can cause many negative human health and environmental effects. While ecosystems are subject to many stresses, including land-use changes, climate change, and variations in hydrologic and meteorologic cycles, the scientific literature has clearly demonstrated that these pollutants can: * Degrade air quality, * Impair visibility, * Damage public health, * Acidify lakes and streams, * Harm sensitive forests, * Harm sensitive coastal ecosystems, and * Accelerate the decay of building materials, paints, and cultural artifacts such as buildings, statues, and sculptures.
Bronze surfaces suffer from corrosion processes if they are exposed outdoors. They are affected by the presence of different aggressive species, the alloy composition and surface preparation. Bronze can be exposed outdoors non-protected or can be pretreated in different ways. Artists use chemical patinations in order to achieve visual effects. In the present study, different finishes were tested on three different patinas: green nitrate, green chloride and an electrochemically prepared patina. The tested finishes were: imidazole and benzotriazole type inhibitors in either ethanol or Paraloid B44, and Carnauba wax as a representative of waxes. The effectiveness of the applied finishes was examined by electrochemical impedance spectroscopy in a solution simulating urban acid rain. Aging experiments were performed in a climatic chamber and a salt spray chamber in order to combine different exposure conditions, the presence of sulphur dioxide, high humidity and a mist of chloride ions. After immersion in an urban acid rain solution, acidified to pH 5, the different patinas were investigated by SEM/EDX and Raman spectroscopy.
Modern organic coatings are complex materials which must be observed and interpreted from the viewpoint of what has become
known as Materials Science. Paints, as most of us first learned to name organic coatings, were originally designed and conceived
as art forms. Visual artists developed their own applied colorants; part of an artist’s success depended on these skills (consider
Leonardo da Vinci). Today, one’s skills as a materials scientist are perhaps the most crucial attributes of the true coatings
scientist. Considering pigmented organic coating as random heterogeneous composite materials was the key to my research group’s
contributions in improving the understanding of pigment volume concentrations (PVC) and critical PVC effects in coatings.
Seeking to develop and improve electrochemical materials characterization techniques for measuring and predicting the corrosion
protective properties of coatings has driven our research at North Dakota State University (NDSU) in this area. Analyzing
the performance of protective coatings for exterior bronze statues and viewing these coatings from the materials requirements
of the art conservator has directed our activities in conservation science. The use of the methods of modern electrochemical
materials science has been the key to our development of Mg-rich primers for entirely Cr-free corrosion protection of aircraft
alloys. Our work on developing methods to perform material measurements directly on coatings during their field use has directed
our recent studies of embedded sensors in coatings. Our work in these areas will be reviewed and current results presented.
Forecasts of future developments in these and other areas of coatings science will be presented, extrapolating from present
developments in materials science. Incorporating materials concerns, especially the methods and concepts of nanomaterials
science, into coatings science will be of paramount importance to future research and development in coatings.
Graphene has exceptional optical, mechanical, and electrical properties, making it an emerging material for novel optoelectronics, photonics, and flexible transparent electrode applications. However, the relatively high sheet resistance of graphene is a major constraint for many of these applications. Here we propose a new approach to achieve low sheet resistance in large-scale CVD monolayer graphene using nonvolatile ferroelectric polymer gating. In this hybrid structure, large-scale graphene is heavily doped up to 3 × 10(13) cm(-2) by nonvolatile ferroelectric dipoles, yielding a low sheet resistance of 120 Ω/□ at ambient conditions. The graphene-ferroelectric transparent conductors (GFeTCs) exhibit more than 95% transmittance from the visible to the near-infrared range owing to the highly transparent nature of the ferroelectric polymer. Together with its excellent mechanical flexibility, chemical inertness, and the simple fabrication process of ferroelectric polymers, the proposed GFeTCs represent a new route toward large-scale graphene-based transparent electrodes and optoelectronics.
A derivation of the noise resistance appropriate to locally stationary electrochemical noise measurements is presented. The equation for noise resistance, R(n) = sigma(v)/sigma(i), where the sigma(v) and sigma(i) values are the standard deviations of the voltage and current noise signals, is shown to be derivable from the low frequency limit of spectral density functions for the potential and current noise. The results are especially pertinent to the study of corrosion in organic coatings/metal substrate systems.
Description d'un traitement préventif de la 'maladie du bronze'. L'objet est plongé dans une solution de 3% en poids de benzotriazole dans de l'alcool, imprégné sous vide et séché. Les objets ainsi traités demeurent stables à une humidité relative de 95%. Le benzotriazole forme une liaison avec le cuivre qui est résistante aux solvants, mais instable dans des conditions acides. Pour le dernier traitement, on recommande une couche de résine 'Incralac'. Le traitement peut être adapté pour les excavations archéologiques, afin de stabiliser immédiatement les bronzes. A cette fin, au lieu du vide, on utilise une solution chaude. /// Viene descritto un procedimento per prevenire la 'malattia' del bronzo: si immerge l'oggetto in una soluzione alcolica di benzotriazolo al 3%; si imbeve sotto vuoto e si essicca. Gli oggetti trattati in questo modo rimangono stabili ad un'umidità relativa del 95%. Il benzotriazolo forma con il rame un legame chimico resistente ai solventi, ma instabile in ambiente acido. Si raccomanda l'uso di un rivestimento finale di resina 'Incralac'. Impiegando una soluzione calda invece del vuoto, si possono stabilizzare immediatamente gli oggetti di bronzo rinvenuti negli scavi archeologici. /// Beschreibung einer Behandlungsmethode zur Verhütung der 'Bronze-Krankeit'. Der Gegenstand wird in eine Alkohollösung mit drei Gewichtsprozent Benzotriazol getaucht, bei Unterdruck imprägniert und dann getrocknet. Auf diese Weise behandelte Gegenstände behalten auch bei 95% relativer Luftfeuchtigkeit ihre Festigkeit. Das Benzotriazol geht eine chemische Bindung mit dem Kupfer ein, das zwar von Lösungsmitteln nicht angegriffen wird, aber nicht säurebeständig ist. Zur abschließenden Behandlung wird eine Beschichtung mit 'Incralac'--Harz empfohlen. Bei archäologischen Ausgrabungsarbeiten kann diese Methode zur sofortigen Behandlung von Bronzegegenständen dahingehend abgewandelt werden, daß man anstelle des Unterdrucks eine warme Lösung verwendet.
Benzotriazole has now been in use for 10 years for the treatment of antiquities made of copper and copper alloys. Its chemistry and theories regarding its mode of action are reviewed, and a bibliography of published work is given. /// On utilise le benzotriazole pour le traitement des objets anciens en cuivre et en alliage de cuivre depuis dix ans. On passe en revue les aspects chimique et théorique de son mode d'action en même temps que l'on donne une bibliographie des publications sur ce sujet. /// Benzotriazol wird jetzt seit 10 Jahren für die Behandlung von Antiquitäten aus Kupfer und Kupferlegierungen benützt. Die Chemie und die Theorien der Wirkungsweise werden erläutert und ein Verzeichnis der veröffenlichten Arbeiten gegeben.
Impedance measurements have been carried out of a number of epoxide coatings on steel in hydrochloric acid solution. The thicknesses of the tested epoxide coatings were similar. For each coating the dependence has been determined of the electric capacitance of the coating in the function of time. By assuming the threshold value of the coating electric capacitance the distribution function of the course of corrosion processes occurring under the coating has been determined. The presented procedure allows a rational evaluation of the protective properties of organic coatings.
Transparent conducting coatings based on doped polyaniline were prepared and characterized. The coatings when laid down on a variety of substrates showed good adhesion. The coated sheets had surface resistance between 1 × 103 to 1 × 109 ohms/sq. and transparency between 40–70%. The coated samples retained their conductivity on exposure to water, common chemicals, and cleaning solvents and are thermally stable to 200°C.
Various electrochemical techniques such as linear sweep voltammetry and electrochemical impedance spectroscopy have proven very useful for the study of electroactive conducting polymers (ECPs). However, such techniques are global in the sense that the measured response is surface-averaged and they are not capable of providing detailed spatial information. Local electrochemical methods, such as local electrochemical impedance spectroscopy (LEIS) and mapping (LEIM) and the scanning vibrating electrode technique (SVET) (also known as the scanning vibrating probe, SVP) have proven very valuable in corrosion research. Such techniques are capable of providing more detailed insight into the mechanism by which ECPs alter the corrosion behavior of active metals. This chapter provides a brief review of local electrochemical techniques, emphasizing the SVET, and presents recent results from our laboratory of SVET studies of various ECPs on active metals. (C) 2003 American Chemical Society.
The long-awaited new edition of the highly renowned 1948 classic, which has been an indispensable resource on corrosion science for generations of engineers. Completely revised and expanded, Uhlig's Corrosion Handbook, Second Edition updates all topics covered in the first edition, then examines new developments in the field, from the use of computers, expert systems, and neural networks for corrosion control to corrosion issues involving the many new materials now in use.
Non stoichiometric thin tin oxide films have been deposited using the PACVD technique in a RF glow discharge diode or triode reactor at low pressure (15 Pa) and at low temperature (25–100°C). The films deposited in the diode configuration were amorphous and presented a high transmittance (95%) in the visible region. The conductivity of the films deposited in the triode configuration can be increased by 4 orders of magnitude with respect to the ones deposited in the diode configuration (from 0.01 to 100 ω−1 cm−1) with a decrease of the gap energy (from 3.5 to 2.5 eV). This increase of the conductivity was accompanied by a slight decrease of the grain size (95 to 45 nm). The very small grain size of the deposited films makes them excellent candidates for gas sensors due to their good sensitivities to different molecules such as ethanol and propane.
After preliminary studies attempting to use electrochemical impedance spectroscopy (EIS) as a method for in situ measurement of the corrosion protective properties of coatings failed, the use of electrochemical noise methods (ENMs) was examined for this purpose. It has been found that a modified version of the electrode configuration that is most commonly used for ENM in the study of coatings involving embedded wires in the coating film allows one to perform in situ measurements of the electrochemical properties of the film. These continuous measurements of electrochemical properties of coatings in exposure are the very first of this type of measurement ever accomplished. The results of our preliminary studies from ENM in an embedded two-electrode configuration are presented. These studies examined the use of embedded electrodes in coatings on exposure in a cyclic salt fog test chamber (Prohesion™ cycle). The test panels under examination undergo exposures that involve changes in temperature, humidity and electrolyte spraying, and are thus a good emulation of exterior exposure. Results are presented for several types of films along with in situ temperature measurements on the test panels under study. An analysis of this data is given which indicates that coating film noise resistance, Rn, decreases as moisture penetrates the film during the “spray cycle”, then rises again during the “dry cycle” in a manner that lags the temperature cycle, while the “localization index” of corrosion as defined by Eden goes through a maximum at the end of the “dry cycle”. This would seem to indicate the internal increase in electrolyte concentration in the film that occurs during drying is one of the key drivers of the transition from low rate general corrosion to the onset of localized corrosion. Implications of the results and the possible uses of the sensing system are also discussed.
Optical quality transparent conducting films of polyaniline (PANI) and of conducting polyblends of polyaniline with amorphous bulk polymers are described. Using functionalized protonic acids to induce solubility in common organic solvents, PANI and PANI-polyblends can be cast from solution, in the conducting form, onto a variety of substrates. The resulting films are clear, and they combine low surface resistance, Rsq, with excellent transparency. By varying the thickness of the film and/or the volume fraction of PANI in the polyblend, the surface resistance and transmittance can be controlled. Colored, highly conducting, optically clear PANI polyblends can be produced, when sulfonic acid dyes are used.
Organic coatings, along with proper surface pretreatment, are the most common and cost effective mode of corrosion protection for metallic objects and structures. From automobiles to jet aircraft, from chemical factories to dishwashers, exterior surfaces of corrodible metals such as steel and aluminum alloys are effectively protected from their environment by a coating system. This role for coatings is historically one of the oldest that coatings have been asked to perform, so the problem of understanding how and why coatings control corrosion is a key issue for coatings science. This topic is especially germane to a symposium in honor of Werner Funke, as he has been one of the leading coatings scientists to have probed this issue both experimentally and philosophically. His unique insight and the questions he has raised have served, and will serve, to guide corrosion/coatings scientists for many years. The key questions for the coatings scientist are still “How and why do coatings protect metallic substrates from corrosion?”, and “How can one improve this protection and its reproducibility?”. These are the questions toward which this paper is directed, questions which were pertinent when first raised by Professor Funke, and are still pertinent today.
Thick, high impedance organic coatings are those class of coatings used to provide corrosion protection to naval vessels, pipelines, gasoline storage tanks, and other large structures such as bridges and plant structures. These coatings, especially the newest generations now being used in practice, can provide exceptional protection and lifetime of performance such that properly and accurately assessing and differentiating among competing coatings is a very difficult task. The standard protocol of salt fog testing (ASTM B117), immersion testing, and outdoor exposure in a corrosive environment with subjective evaluation of a coating's performance durings and after testing, does not adequatcly rank and predict coating lifetimes for new coating systems, especially for the environmentally compliant coating systems such as powder coatings (especially the thick, fusion bonded epoxy (FBE) coatings used for pipelines), two component epoxy and urethane coatings and waterborne coatings. New, objective test methods are desperately needed by users and manufacturers of coatings. A relatively new electrochemical test procedure, electrochemical noise methods (ENM), as developed by Skerry and Eden, has been shown in our laboratory to be very successful in the ranking and prediction of relative coating performance. We have used the method successfully on naval ship coatings, several pipeline coatings and other related systems, and Skerry has used them successfully on industrial maintenance coatings. We have used these methods in conjunction with electrochemical impedance spectroscopy, d.c. resistance measurements and cyclic salt fog testing of the ProhesionTM type. In our studies of pipeline coatings, we needed to investigate thermal effects because of their extended range of use temperature. In these studies, we have discovered that electrochemical methods can be used for an in situ measurement of the Tg of coatings in electrolyte immersion. Further, the ‘plasticizing’ effect of aqueous electrolyte absorption as well as its relative irreversibility has been shown. For all coatings studied, ENM provided useful, objective, numerical data which rapidly ranks coatings and provides useful information on the relative lifetime prediction of coatings which may provide up to 30 years of service.
Fluoropolymer coatings, particularly those based on polyvinylidene fluoride (PVDF) resins, have a 35 year history of outstanding performance in outdoor applications. However, the chemical inertness of PVDF presents challenges to the paint formulator in that it prevents adhesion to substrates and makes it difficult to disperse pigments. To overcome these difficulties, an acrylic modifier resin is usually added to the PVDF resin. The acrylic modifier is traditionally physically blended with the PVDF resin to improve coating adhesion and enhance pigment dispersion. The physical blending results in a PVDF/acrylic mixture on a macro-molecular scale. ATOFINA Chemicals, Inc. has developed a novel approach to mix the fluoropolymer and acrylic on micro-molecular scale. Because of this intimate mixing, and the wide latitude of the acrylic and fluoropolymer monomers that can be utilized, a wide range of unique properties can be achieved in solvent-base dispersion coatings, and water-borne coatings. The unique properties of the solvent-base and water-borne coatings are discussed in this paper.
One possibility to obtain transparent, electrically conductive materials is the crystallization of conducting charge-transfer-complexes (CT-complexes) in a polymer matrix in the form of needle-or dendrite-like structures. With tetraselenotetracene chloride ((TSeT)2Cl), a radical cation salt, as electroconductive filler, we have access to a thermally stable, highly conductive material, with values of the bulk conductivity of the composite material up to 1 S/cm at a loading of the conductive complex below 1 %(w/w).The preparation of such composite structures as free standing (cast) films and in the form of very thin coated layers is presented and their electrical, optical and mechanical properties are discussed. In addition we show their potential use for display electrodes, transparent heating elements, and for antistatic applications.
Thesis (Certificate in Conservation)--Fogg Art Museum. Center for Conservation and Technical Studies, 1986. Includes bibliographical references.
Research into protective coating systems for outdoor bronze sculpture and ornamentation, Phase II, Final Report to the NCPTT
- L Brostoff
- T Shedlosky
- E René De La Rie
L. Brostoff, T. Shedlosky, E. René de la Rie, Research into protective
coating systems for outdoor bronze sculpture and ornamentation,
Phase II, Final Report to the NCPTT 1997 and 1998 Grant Program.
Research into protective coating system for outdoor sculpture and ornamentation
- L B Brostoff
- E René De La Rie
L.B. Brostoff, E. René de la Rie, Research into protective coating
system for outdoor sculpture and ornamentation, in: I.D. MacLeod,
et al. (Eds.), METAL 95, Semur en Auxios, France, James & James
Ltd., London, 1997, pp. 242-244.
Prohesion compared to salt spray and outdoors: cyclic methods of accelerated corrosion testing, Presentation at Federation of Society for Coatings Technology
- N D Cremer
N.D. Cremer, Prohesion compared to salt spray and outdoors: cyclic
methods of accelerated corrosion testing, Presentation at Federation
of Society for Coatings Technology 1989 Paint Show.
Copper and Bronze in Art Corrosion, Colorants, Conservation
- D Scott
D. Scott, Copper and Bronze in Art Corrosion, Colorants,
Conservation, 1st ed., Getty Publications, Los Angeles, CA, 2002.
The conservation of outdoor bronze sculpture: a review of modern theory and practice, AIC Preprints, The American Institute for Conservation of Historic and Artistic Works
- P D Weil
P.D. Weil, The conservation of outdoor bronze sculpture: a review of
modern theory and practice, AIC Preprints, The American Institute
for Conservation of Historic and Artistic Works, San Francisco, 1980.
The Care of Bronze Sculpture
- P V Kipper
P.V. Kipper, The Care of Bronze Sculpture, 2nd ed., Path Publications
and Rodgers & Nelsen, Loveland, CO, 1998.
Electrochemical studies of the protection of bronzes by organic coatings
- G Bierwagen
- T Shedlosky
- L Ellingson
G. Bierwagen, T. Shedlosky, L. Ellingson, Electrochemical studies
of the protection of bronzes by organic coatings, Presented at ICC-COM-UNESCO Metal 2001, Congress Mundial de Conservacion de
Metales, Metals Working Group International Congress, Santiago,
Chile, April 2-6, 2001.
Electrochemical noise for evaluation of coatings on museum artifacts
- A Wain
- J Alverez
- T H Randle
A. Wain, J. Alverez, T.H. Randle, Electrochemical noise for
evaluation of coatings on museum artifacts, in: Proceedings of
the 13th International Corrosion Congress, Paper 126, Melbourne,
Australia, November 1996, p. 669.
Development and testing of organic coatings for the protection of outdoor bronze sculpture from air-pollutant enhanced corrosion-year 2, Final Report to the NCPTT
- G P Bierwagen
- T Shedlosky
- L Ellingson
G.P. Bierwagen, T. Shedlosky, L. Ellingson, Development and testing
of organic coatings for the protection of outdoor bronze sculpture
from air-pollutant enhanced corrosion-year 2, Final Report to the
NCPTT 1999 and 2000 Grant Program.
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- J Cambell
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- M Tullmin
- P R Roberge