Mario G S Ferreira

University of Aveiro | UA · Department of Materials and Ceramics Engineering

Layered double hydroxides (LDHs) have gained attention in the concrete research field, appearing as prospective additives for controlling chloride attack, and as micro or nano deliverers of corrosion inhibitors. This work reports the effect of ZnAl-NO2 LDH on the evolution of chloride concentration in the pore solution and on the corrosion resistan...

This study reports the development of anticorrosive bilayer coatings consisting of in situ grown layered double hydroxides (LDH) covered with a polyurethane layer on a steel substrate. This design aims at providing corrosion protection via the controlled release of gluconate from LDH near the substrate, while at the same time contributing to the im...

In this study, the corrosion resistance of AA2024-T3 specimens anodized in TSA and subsequently post-treated in a Ce-H2O2 solution and sealed by a hybrid sol–gel coating (3-glycidoxypropyltrimethoxysilane and tetraethoxysilane), with hydrolysis solution aging times of up to 6 months, was investigated by means of electrochemical impedance spectrosco...

Carbon-based reinforcements are widely used in composite materials for a wide range of applications including wind energy and transportation. In the later, the carbon-fiber reinforced polymers (CFRP) components are often joined together with metallic parts creating conditions for galvanic corrosion. Therefore, a deeper understanding of the electroc...

The detection of corrosion at early stages could increase the service life of metal-based infrastructures in a cost-effective manner. Despite the recent progress in “smart” self-reporting corrosion sensing coatings, the development of environmentally friendly systems appropriate for steel substrate used in offshore applications remains a relevant c...

This work describes the main advances carried out in the field of corrosion protection using layered double hydroxides (LDH), both as additive/pigment-based systems in organic coatings and as conversion films/pre-treatments. In the context of the research topic “Celebrating 20 years of CICECO”, the main works reported herein are based on SECOP’s gr...

Nanometric layers of Al2O3 were applied by atomic layer deposition (ALD) on 2024-T3 aluminium alloy. The ALD layers suppressed the corrosion of the alloy as confirmed by Scanning Kelvin Probe Force Microscopy (SKPFM), polarization curves and Electrochemical Impedance Spectroscopy (EIS). The protection provided by the ALD layers weakened with the ti...

The direct ZnAl layered double hydroxide growth on AA2024 is a fast-occurring reaction, yet is characterized by an inhomogeneous film thickness. It has been shown that at the periphery of Cu-rich intermetallic, the flakes tend to be larger and denser. A combination of in situ and ex situ measurements were used to monitor the changes in the layered...

The sulfuric acid attack is a common form of degradation of reinforced concrete in contact with industrial wastewater, mine water, acid rain, or in sewage treatment stations. In this work, new pH-sensitive IrOx electrodes were developed for monitoring the pH inside mortar or concrete. To test their ability, the pH sensors were embedded in mortar sa...

Alginate (ALG) is a natural polymer used in a wide range of applications. Cerium is a sustainable corrosion inhibitor for many metal substrates. In this study, ALG/Ce3+ hydrogel microparticles are presented as an innovative cerium(III) reservoir system for the smart release of cerium ions. The active corrosion inhibition capacity of the ALG/Ce3+ co...

In a quest for a better understanding of the mechanism and contribution(s) of fresh (“un-degraded”) and degraded CFRP surfaces to galvanic corrosion of coupled metals in multi-material assemblies the electrochemical behaviour of CFRP in quiescent 50 mM NaCl was studied using electrochemical techniques. Tests using ferricyanide/ferrocyanide redox co...

The effect of a post-treatment for short time in 50 mM Ce(NO3)3 solution, with or without H2O2, on the corrosion of AA2024-T3 anodized in tartaric-sulfuric acid was investigated. Electrochemical (EIS, polarization curves) and corrosion (immersion) tests showed improved performance for samples post-treated at 50 oC in the H2O2 containing solution. M...

Sodium carboxymethylcellulose (CMC-Na) microparticles, containing corrosion inhibitor benzotriazole (BTA), were prepared using different spray drying processing parameters, with the purpose of future application in protective coatings for the delivery of corrosion inhibitors. The effects of the processing parameters, such as inlet temperature and s...

Corrosion protection and surface properties of Magnesium (Mg) containing 51ppm Fe (HP-Mg) and 341 ppm Fe (CP-Mg) were assessed by EIS, AFM/SKPFM, and photoluminescence spectroscopy in NaCl solutions with/without fumarate (Fum), 2,5-pyridinedicarboxylate (PDCA) and salicylate (Sal) carboxylates. The PDCA was effective in corrosion inhibition of HP-M...

Layered double hydroxides (LDH) have emerged as an alternative to chromates for corrosion protection by exploiting anion-exchange phenomena: the LDH releases corrosion inhibitor anions and captures the corrosive agent anions, extending the metal surface lifetime. In this work, the main aim was to promote continuation of corrosion protection after t...

MgCa and MgGd series of alloys are often reported as promising candidates for biomedical applications. In the present study, cytotoxicity and corrosion behavior of Mg1Ca and Mg10Gd alloys in different electrolytes (NaCl, PBS, MEM) have been investigated in order to make a direct comparison and understand the mechanisms behind their performance. Pot...

In this work metallic pins made of Mg5Gd alloy were coated with magnetron sputtered PVD Mg5Gd layers. Immersion tests in Hank’s balanced salt solution (HBSS) were performed. The PVD coating drastically reduced the corrosion rate of the Mg5Gd pin. The corrosion mechanism of the coating was studied in model electrochemical measurements by Scanning Vi...

This work compares different electrodeposition procedures to produce nickel black coatings as greener and less toxic alternatives to Cr(VI)-based coatings used in different applications. Nickel and nickel-plated brass served as substrates in studies with a Hull cell and polarization curves. After a set of comparative experiments, the best electrode...

A proper assignment of time constants is important for the correct interpretation of the electrochemical impedance spectra of coated substrates. In this work several model aluminium samples with different anodic oxide thicknesses were prepared and characterised. The aluminium samples were coated by a hybrid sol-gel formulation and studied by electr...

In this work the ZnAl-NO2 LDH (layered double hydroxide) is investigated as a possible additive for mitigating the chloride-induced corrosion of steel in reinforced concrete. The investigation focused on the stability and chloride binding capacity of this LDH in the pH range typical of cementitious materials. Until pH = 12.5 the material was stable...

A surface layer separating the metal from the environment is often the simplest method of corrosion control. This chapter presents an overview of the coatings used for protecting metals against corrosion, with emphasis on emergent “smart” and self-healing coatings. This chapter begins with a general view of the metallic corrosion process, mechanism...

The scanning vibrating electrode technique (SVET) measures the electrical field in electrolyte solutions associated with the ionic currents flowing therein. When this is done close to a metallic surface it can sense the currents due to corrosion and detect defects in paint films. This chapter presents the basis of the technique, shows examples of i...

Smart protection of metallic materials is currently a hot topic in mitigation of corrosion of metallic structures, and promises reduction in both economic and environmental costs. Degradation of carbon-reinforced composite materials and CFRP-Metal joints is a serious issue in high-performance weight-optimized structures employed in the aeronautical...

Ni-Cr-Mo is a candidate to substitute Co binders in WC-based composites, where high corrosion resistance is required. This work focused on the effect of Cr on the corrosion susceptibility of WC-Ni-Cr-Mo composites, in acid media. Specimens were produced by powder metallurgy followed by microstructural, chemical and mechanical characterization. Open...

The search for new alternatives to replace chromate-based coatings is a matter of great importance. Since their official ban due to the raised concerns of hexavalent chromium to the human health and the environment, significant efforts have been devoted to finding a more suitable alternative for the corrosion protection of aluminum alloys. However,...

Deep eutectic solvents have been widely acknowledged as ionic liquid analogues, since they share many characteristics and properties with ionic liquids. The two major application areas of deep eutectic solvents have been metal processing and synthesis media; however, plenty of other applications have already been reported and predicted for these li...

Kinetics parameters for three anion exchange reactions - Zn-LDH-NO3 → Zn-LDH-Cl, Zn-LDH-NO3 → Zn-LDH-SO4 and Zn-LDH-NO3 → Zn-LDH-VOx - were obtained by in situ synchrotron study. The first and the second ones are two-stage reactions; the first stage is characterized by the two-dimensional diffusion-controlled reaction following deceleratory nucleat...

Concrete possesses an intrinsic chloride binding capacity. Chloride ions from the environment bind with the hydrated cementitious phases in the form of bound chlorides. The contribution of chemically bound chlorides toward increasing the service life of concrete structures is vital as they help in slowing down the chloride diffusion in the concrete...

This work describes the synthesis and characterization of Zn‐Al and Mg‐Al layered double hydroxides (LDHs) intercalated with hexacyanoferrate. X‐ray diffraction, infrared spectroscopy and scanning electron microscopy indicated a successful intercalation of hexacyanoferrate in the sub‐micrometer sized platelet‐like particles. Release studies of hexa...

This work investigated the use of ZnAl-layered double hydroxide (LDH) intercalated with nitrate or nitrite ions for controlling the corrosion of steel in reinforced concrete. The work started by analyzing the stability of the powder in the 1–14 pH range and the capacity for capturing chloride ions in aqueous solutions of different pH. The effect of...

Kinetics parameters for three anion exchange reactions - Zn-LDH-NO3 - Zn-LDH-Cl, Zn-LDH-NO3 - Zn-LDH-SO4 and Zn-LDH-NO3 - Zn-LDH-VOx - were obtained by in situ synchrotron study. The first and the second ones are two-stage reactions; the first stage is characterized by the two-dimensional diffusion-controlled reaction following deceleratory nucleat...

Biopolymeric microspheres containing corrosion inhibitor benzotriazole (BTA) were prepared by a spray-drying technique using carboxymethylcellulose (CMC-Na) as encapsulating material. The resulting microspheres were characterized by FTIR, TGA, SEM and TEM analysis. Microspheres containing BTA have an average diameter of 1.1 μm. FTIR analysis confir...

Chitosan microspheres containing bromocresol green, cresol red, and phenolphthalein for corrosion detection, through pH change, are synthesized in order to be used in protective coatings for aluminium alloys. Microspheres containing corrosion detection species are characterized morphologically (SEM) and physico‐chemically (FTIR, TGA). Release studi...

Rare earth ions are amongst the most promising new generation corrosion inhibitors. This communication describes conditions where, instead of inhibition, acceleration of corrosion occurs after rare earth salts are added to solution. The work was carried out mainly with the Fe-Zn galvanic couple and different rare earth salts, using electrochemical...

Benzotriazole (BTA) release from a layered double hydroxide based on Zn and Al (LDH-ZnAl/BTA) in a saline solution was investigated using UV-Vis spectroscopy, and corrosion protection was studied by OCP and EIS measurements on carbon steel samples immersed in 3.5 wt-% NaCl solution. The corrosion protection of this ion-exchanger material performanc...

The dissimilarities and features of the crystal structure of ZnAl LDH-NO3 conversion layers grown directly on pure zinc and aluminum alloy 2024 were investigated in the present paper. Although the nature of the cations in the double hydroxides are the same in both cases (Al³⁺ and Zn²⁺), their sources differ according to the substrate. This leads to...

The advantage of using magnesium alloys over traditional metals, biodegradable polymer and ceramics lies on their superior mechanical properties and their biocompatibility and biodegradability. This advantage makes them suitable for biomedical applications but prone to corrosion, therefore their biggest advantage is simultaneously a challenge. Magn...

WC-Ni-Cr-Mo are good candidates for replacing WC-Co for its better corrosion performance. This work investigated the effect of different Mo content on the mechanical properties and corrosion susceptibility of WC-Ni-Cr-Mo composites in chloride and sulphate acidic media. Chemical, microstructural, and electrochemical analysis were performed. Results...

The objective of this work is to investigate the scale of the effect of spontaneous solution evaporation during SVET (Scanning Vibrating Electrode Technique) measurements and demonstrate how it biases the final results. When SVET maps are continuously acquired for more than several hours, the measured currents are smaller than expected. This is att...

Single-phase magnesium-aluminium layered double hydroxide (LDH) intercalated with dihydrogen phosphate was successfully produced by hydration of nanopowder of the respective mixed metal oxide (MMO) obtained using sol-gel based method followed by a two-step anion exchange hydroxide-to-chloride and chloride-to-phosphate. The MMO with the metal cation...

High-quality stoichiometric Co2Al–NO3 and Co2Al–CO3 layered double hydroxides (LDHs) have been obtained by precipitation followed by anion exchange, both high-power-sonication assisted. Application of high-power ultrasound has been demonstrated to result in a considerable acceleration of the crystallization process and the anion-exchange reaction....

Layered double hydroxides (LDHs) intercalated with corrosion inhibitive species are considered as promising additives to protection coatings. However, the conventional method of LDH preparation via co-precipitation followed by anion exchange is a water consuming and slow process hardly applicable to industrial use. In this work, a novel approach to...

This work reports a novel approach for growing layered double hydroxide (LDH) films on any plasma electrolytic oxidation (PEO) coated AA2024 independently of the nature of the PEO coating. The specific PEO coating chosen to carry out this work is considered to be not suitable for direct LDH growth because of phase composition and morphological feat...

The successful preparation of the titania nanotubular layers (TNT) in different deep eutectic solvent based electrolytes was performed in the current work. Choline chloride based deep eutectic solvents with various hydrogen bond donors, such as ethylene glycol, urea and malonic acid were used. All results were compared with standard ethylene glycol...

The specific microstructure of aluminum alloys is herein explored to grow spatially-resolved layered double hydroxide (SR-LDH) clusters on their surface. Upon chemical modification of LDHs via intercalation, adsorption and grafting with different functional molecules, novel surface-engineered surfaces were obtained. Crystal structure and phase comp...

Carbon is used as a reinforcing phase in carbon-fiber reinforced polymer composites employed in aeronautical and other technological applications. Under polarization in aqueous media, which can occur on galvanic coupling of carbon-fiber reinforced polymers (CFRP) with metals in multi-material structures, degradation of the composite occurs. These d...

Suppression of electrochemical activity (cathodic activity) on CFRP surface at cathodic potentials consistent with galvanic coupling of CFRP with active metals like aluminium and zinc have been demonstrated by electrochemical treatment of CFRP surface in the presence of sodium dodecyl sulphate (SDS). Modification to the CFRP surface by SDS adsorpti...

A synthesis method and growth mechanism for ZnAl–NO 3 LDH conversion coatings on zinc is presented for the first time.

Siloxane-poly(methyl methacrylate) (PMMA) hybrid was synthesized based on the sol-gel method and applied to Ti-6Al-4V through dip-coating. The structural feature of the hybrid was subjected to Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TG); its morphological properties were analyzed through scanning electron micr...

Encapsulated metal nanostructures were prepared using the powerful pulsed discharge method. Metal nanorods were obtained in porous titania and alumina matrix by direct electrodeposition from 1-ethyl-3-methylimidazolium chloride-based ionic liquids. The deposition process was characterized by cyclic voltammetry. Morphology of the encapsulated struct...

A numerical model for enhanced service life prediction of concrete infrastructure is presented which includes transient analysis of processes during corrosion initiation as well as propagation stage. The temporal and spatial transition of Steel–Concrete Interface during depassivation events is described by a randomly varying chloride threshold func...

In the frame of the current work, it was shown that plasma electrolytic oxidation (PEO) treatment can be applied on top of phosphoric sulfuric acid (PSA) anodized aluminum alloy AA2024. Being hard and well-adherent to the substrate, PEO layers improve both corrosion and wear resistance of the material. To facilitate PEO formation and achieve a dens...

Cobalt is the standard binder in tungsten carbide (WC) hardmetals due to its compatibility with the WC phase, resulting in composites with exceptional hardness and wear resistance. However, their corrosion resistance is not satisfactory in many applications, leading to the early deterioration and failure of tools and equipment. In this work, the co...

In this work active corrosion protection of AA2024 by a bilayer system consisting of a LDH (layered double hydroxides) conversion layer coated by a sol-gel film was studied. Impedance and Scanning vibrating electrode technique (SVET) studies demonstrated an efficient active corrosion protection and self-healing abilities of the systems containing L...

This chapter provides an overview of corrosion protection strategies using sol-gel coatings. The chapter starts by acknowledging current state of corrosion engineering and main directions in corrosion protection of metals specifically addressing how sol-gel systems differ from other coatings types. The examples of application of sol-gel coatings as...

Mg3/Al1 and Mg3Al1-xTbx layered double hydroxides (LDHs) intercalated with terephthalate anion were synthesized using sol-gel method. The obtained materials were characterized by X-ray diffraction (XRD) analysis, infrared (FTIR) spectroscopy, fluorescence spectroscopy (FLS) and scanning electron microscopy (SEM). The Tb³⁺ substitution effects in th...

It is critical for the aeronautical industry that the next generation of smart coatings allows the early detection and continuous monitoring of corrosion. Once corrosion is detected, preventive actions can be taken in order to mitigate its costs. Our strategy relies on functional coatings capable of detecting metallic corrosion early on. After appr...

Encapsulated metal nanostructures were prepared using the powerful pulsed discharge method. Metal nanorods were obtained in porous titania and alumina matrix by direct electrodeposition from 1-ethyl-3-methylimidazolium chloride-based ionic liquids. The deposition process was characterized by cyclic voltammetry. Morphology of the encapsulated struct...

Mg/Al/Ln (Ln = Nd, Sm, Eu) layered double hydroxides (LDHs) were synthesized using sol–gel method for the first time to the best our knowledge. The obtained materials were characterized by X-ray di raction analysis and fluorescence spectroscopy. The phase composition and luminescent properties of these LDHs were investigated and discussed. The Ln³⁺...

The compatibility between nanocontainers and coating formulations is perhaps the last frontier in the quest for functional coatings. Sensing coatings for early metallic corrosion detection is an urgently needed technology by aeronautical companies to mitigate the costs of corrosion through continuous monitoring. In this work, we revisit phenolphtha...

Magnesium–aluminium–bismuth-layered double hydroxides (LDH) intercalated with carbonate were studied in respect of maximal rate of substitution of Al³⁺ by Bi³⁺ for the first time. LDH with the nominal compositions of Mg3Al1 - x Bix –CO3 (x = 0 to 0.5) were prepared using both the conventional super saturation co-precipitation method and sol–gel pro...

WC-AISI304 (SS) composites with the phase composition controlled by adequate carbon addition are being developed as potential alternatives to the established WC-Co hardmetals, following the REACH regulation relatively to the elimination of toxic and critical elements and the actual market demands of lower cost production and enlarged range of prope...

This paper presents an introduction to the Scanning Vibrating Electrode Technique (SVET) and its application to corrosion research. Up to now it has been impossible to find a single work that could provide a simple and comprehensive introduction to this technique, giving a clear idea of what SVET is, how it works, the possibilities and limitations....

The tinplate, used in the packaging sector and formed from a metal substrate, comprises a steel base which has undergone a surface treatment to produce a thin layer of FeSn2, a tin layer and an oxide tin layer. Currently, packaging using surface treatment is based on the use of chromates because these metals provide an excellent corrosion resistanc...

Microcapsules containing linseed oil were synthesized by in situ polymerization method and benzotriazole was entrapped between polyelectrolytes layers assembled outside the microcapsules, using the Layer-by-Layer technique. The prepared microcapsules presented mean number diameter of 2.08 μm and released greater amount of benzotriazole in slightly...

Magnetic behavior of CoII(n)AlIII layered double hydroxides (LDHs) (n = Co/Al = 2 and 3) intercalated with nitrate was studied as a function of temperature. Both LDH compounds are paramagnetic above about 8 K. A rapid increase of their magnetic moments occurs below this temperature until the moments reach the maximum values at Tmax of 4.0 K and 3.2...