[Show abstract][Hide abstract] ABSTRACT: Background: Ethanolic solutions of long-chain carboxylic acids can be applied to lead metal substrates to form a coating of lead carboxylate which provides protection against atmospheric pollutants. Results and conclusions: In this paper we describe the optimal inhibitor concentration for the coating on lead. Electrochemical impedance data taken before and after immersion in media modelling oak emitted volatile organic compounds (VOCs) polluted atmospheres show that coating effectiveness decreases after exposure, but the effect is lessened if longer chain carboxylates are used.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: Capillary–based microcells, also known as
microcapillary electrochemical droplet cells, have proved their
capabilities in various electrochemical surface investigations
in recent decades. Due to the large measured current density
and the high limiting current, this technique provides high–
resolution electrochemical responses. Current densities in the
range from a few femto to pico Acm−2 to hundreds of Acm−2
can be measured using this technique. Various applications for
microcapillary cells have been reported. Technical limitations,
such as the Ohmic drop and changes in the composition of the
measurement area near the tip of the microcapillary have also
been considered by some researchers. The rapid increase in
the application of microcells and the increase in the number of
related reports published in the literature have paralleled recent
attempts to develop and improve microcell setups, showing
that this technique is already well established for electrochemical
Journal of Solid State Electrochemistry 01/2014; · 2.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Polarization and impedance measurements in a corrosive environment have been used to investigate the adsorption and corrosion inhibition characteristics of sodium dodecanoate on lead. Results show that the concentration of sodium dodecanoate has an important effect on the anodic lead dissolution. Monolayer adsorption occurs at low inhibitor concentrations. The equilibrium constant (Kads), calculated using the Frumkin model, is about 10−5 M−1. Multilayer formation at concentrations above the critical micelle concentration ensures the formation of a lead dodecanoate coating following the dissolution-precipitation mechanism. These lead complexes are formed on top of the surface, which has been conﬁrmed by secondary electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS).
Journal of The Electrochemical Society 01/2014; 161(3):C126-C137. · 2.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In order to understand the corrosive and morphological characteristics of lead dodecanoate protective coatings on real samples, three pipe organ samples were studied using optical microscopy (OM), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). The corrosion products and elemental composition of the top layer of the different pipe organ samples were investigated. The results indicate that the three pipe organ samples are made of an alloy composed mainly of lead and tin. After immersion and the deposition of the protective coating, only lead and no tin is detected, which indicates the formation of a thick coating containing lead dodecanoate complexes.
[Show abstract][Hide abstract] ABSTRACT: Objective
To assess the site-specific corrosive behaviour of the frameless IUD following long-term exposure to the uterine environment.
A qualitative and morphological study using X-ray diffraction (XRD) and scanning electron microscopy (SEM).
Three GyneFix® IUDs which were in site up to 150 months were examined. In utero corroded copper sleeves were divided into 10 different groups based on their shape (U or O), orientation (inside or outside) and in utero residence time. X-ray diffraction indicated the presence of solely cuprite (Cu2O) as corrosion product on both the inside and the outside of the copper sleeves, regardless of their shape. These results were confirmed by backscattered electron micrographs recorded on the inside, the outside and the cross-section of the IUD sleeve. SEM results suggest that shape and orientation slightly affect the corrosion rate.
The apparent copper loss from both sides of GyneFix copper tubes proves that both sides are a potential copper source and therefore justifies the design of GyneFix IUD. This could be beneficial for women as the IUD could be reduced in size and therefore better tolerated. The impact on bleeding could also be minimized.
[Show abstract][Hide abstract] ABSTRACT: In experiments preliminary to the design of an x-ray excited optical luminescence (XEOL) based chemical mapping tool we have used x-ray micro (4.5 μm × 5.2 μm) and macro (1 mm × 6 mm) beams with similar total fluxes to assess the effects of a high flux density beam of x-rays at energies close to an absorption edge on inorganic surfaces in air. The near surface composition of corroded cupreous alloys was analysed using parallel x-ray and optical photoemission channels to collect x-ray absorption near-edge structure (XANES) data at the Cu-K edge. The x-ray fluorescence channel is characteristic of the composition averages over several microns into the surface, whereas the optical channel is surface specific to about 200 nm. Whilst the x-ray fluorescence data were mostly insensitive to the x-ray dose, the XEOL-XANES data from the micro beam showed significant dose-dependent changes to the superficial region including surface cleaning, changes in the oxidation state of the copper, and destruction of surface compounds responsible for pre-edge fluorescence or phosphorescence in the visible. In one case there was evidence that the lead phase in a bronze had melted. Conversely, data from the macro-beam were stable over several hours. Apart from localized heating effects, the micro-beam damage is probably associated with the O3 loading of the surface and increased reaction rate with atmospheric water vapour.
[Show abstract][Hide abstract] ABSTRACT: We report the use of voltammetry of immobilized microparticles for the quantification of metallic copper and nickel in their binary mixtures. Twenty-two electrolytes were investigated in order to obtain well-separated oxidation peaks. An experimental design strategy was employed to study the effect of the electrolyte concentration and the scan rate on the resolution of the oxidation peaks. With the optimum experimental parameters, a quantification was performed and the linear results of percentage of anodic currents in term of their relative amount in the binary mixture were obtained. Finally, the prediction of two mixture samples was performed and gave satisfactory results.
International journal of electrochemical science 02/2013; 8:2576 - 2585. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Tetra-substituted palladium phthalocyanine complexes with different electron withdrawing and electron donating substituents (–H, –NO2, –NH2, –Cl, –COOH, aryl thio) have been synthesized with a good yield. The synthesized complexes were characterized using XPS, UV–Vis, IR, Raman, XRD, TGA and electrochemistry. The XPS spectra show that the central metal ion is in the +2 state, while the UV–Vis spectra demonstrate split absorption peaks in the Q-band region 600–700 nm due to the presence of dimeric and oligomeric molecules in addition to the monomeric species. The UV–Vis and Raman spectra demonstrate a shift in the peaks/bands which is a result of the electron withdrawing and electron donating substituents at the periphery of the benzene ring compared to the parent palladium phthalocyanine. The thermogravimetic stability studies show that these complexes undergo two separate decomposition processes. The thermal stability for different complexes are in the order: PdPc < PdTPSPc < PdTClPc < PdTAPc < PdTCAPc = PdTNPc, indicating that the substituents at the periphery have an effect on the thermal stability. The cyclic voltammetric data in DMSO show that the central metal ion Pd does not undergo a redox process and the redox behaviour observed is mainly due to the macrocyclic ring reduction process.
Dyes and Pigments 01/2013; 96(1):269–277. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Electrochemical impedance measurements have been used to investigate the influence of the deposition method, including time and temperature, upon the corrosion inhibition characteristics of lead dodecanoate coatings on lead electrodes. The results were analysed using multivariate statistics and show that, in general, these easily prepared coatings are very protective against corrosion. The temperature proves to be an important parameter for the quality and the corrosion inhibition efficiency of the coating. A comparison between two different electrochemically assisted deposition methods, immersion using a reduction pretreatment and cyclic voltammetry, does not show significant differences. Using the immersion technique at room temperature, the deposition time was tested as the third influencing parameter for the corrosion inhibition efficiency of the deposited lead dodecanoate coatings. A longer deposition time of the lead into the sodium dodecanoate solution provides a layer with a somewhat higher corrosion resistance.
Journal of Solid State Electrochemistry 01/2013; 17(5). · 2.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 304L stainless steel was cathodically polarised in a 1 M sodium chloride solution using a microcapillary electrochemical droplet cell. During the cathodic polarisation the produced hydrogen atoms penetrate into the sample and accumulate at sites of the steel surface. We observed that the pitting potential (Epit), the anodic current density (Icorr) and the corrosion potential (Ecorr) of the polarised steel are strongly influenced by the applied cathodic potential and therefore by the amount of charged hydrogen atoms which penetrate into the sample. Local electrochemical impedance spectroscopy (LEIS) using different applied cathodic potentials shows lower corrosion resistance for cathodically polarised steel and reveals a different behaviour on a microscale level.
International journal of electrochemical science 09/2012; 7:8007 - 8019. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have developed and tested two complementary methods for making time-lapse synchrotron X-ray diffraction (XRD) measurements of the growth of synthetic corrosion layers using a protocol for producing copper(I) chloride (nantokite), on copper as a test. In the first method, a copper coupon was spin-coated with saturated copper(II) chloride solution in air while the surface was characterized in real time using XRD with a fast one-dimensional (1-D) detector. In the second, a droplet of the same reagent was suspended from an X-ray-transparent window in a hermetically sealed cell and the coupon was brought into contact with this while XRD diffractograms were acquired with a charge-coupled device (CCD) camera. The protocol is completed by a deionized water rinse, which was also studied. The XRD shows nantokite precipitation in solution as well as growth on the surface, but the end products were variable proportions of nantokite, cuprite (Cu(2)O), and paratacamite (Cu(2)(OH)(3)Cl). The latter two were observed forming in a reaction between the nantokite and the rinsing water. Comparisons between samples analyzed in the synchrotron and at lower power densities show that the effects of any radiolysis or slight heating of the sample are insignificant in this case. It would be simple to extend these methods to other corrosion or surface reaction systems.
[Show abstract][Hide abstract] ABSTRACT: An aqueous sodium dodecanoate solution has been used for the formation of a protective coating for lead. Three deposition methods have been compared: immobilization using cyclic voltammetry, immersion and amperometry. Apart from this, we tested a reduction pretreatment of the lead surface (−1.5 V during 600 s) in order to obtain a more reproducible coating, resulting in a better corrosion protection behavior. The corrosion inhibition properties were examined using potentiodynamic polarization curves and electrochemical impedance measurements in a standard corrosive environment.
Progress in Organic Coatings 05/2012; 74(1):1–7. · 2.30 Impact Factor