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The interfacial bonding properties of succinic acid, myristic acid, and succinic anhydride molecules with a set of differently pretreated zinc samples have been investigated using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The molecules were selected to model the typically used carboxylic-based adhesives, coatings, and self-assembling monolayers. The differently pretreated oxidized zinc surfaces were found to be capable of adsorbing the monomers, resulting in the formation of carboxylates. The interactions between the three types of monomers and the zinc samples resulted in the formation of a bridging bidentate coordination state on all samples, implying the contribution of the same functional groups in the adsorption mechanism. Moreover, relative FTIR peak intensities were utilized to evaluate the molecular structures upon adsorption. It was found that a sufficiently positive potential promoted an interaction between the adsorbates depending on the applied experimental parameters. The interactions resulted in a structural rearrangement of the molecules and formation of different end groups. The structural variations are expected to represent different interfacial characteristics of the polymer coatings.

A new, simple chemical route was developed for the synthesis of pure nanocalcite crystals by controlling the reaction of an aqueous solution of CaO and CO2 gas. Results revealed formation of well-defined and pure nanocalcite crystals with controlled crystallite and particle size, without additives or organic solvents. The crystallite and particle size can be controlled, and smaller sizes are obtained by decreasing the CaO concentration and increasing the CO2 flow rate. The decrease of crystallite and particle size below a certain threshold provides the nanocalcite crystal signature characteristics that can be clearly observed in XRD patterns, TEM images, FTIR spectra, Raman spectra, XPS spectra, and thermal stability measurements.

The electrochemical and microstructural properties of the clad and core from a modified AA3xxx/AA4xxx brazing sheet were investigated before and after brazing. For this, scanning Kelvin probe force microscopy (SKPFM) and field emission electron probe micro analysis (FE-EPMA) were used. The Volta potential difference (VPD) was measured as a function of depth for the brazed and non-brazed sheets. This was correlated with the cross-sectional variation of chemistry and microstructure that result from brazing. Furthermore, potentiodynamic polarization experiments and subsequent microscopic analysis of the corroded samples were used to explore the corrosion mechanism of the modified brazed sheet. The investigation revealed that the major consequences of brazing for the microstructure are: an increase in the Si content of the matrix in the heat affected zone (HAZ); a non-uniform distribution of Cu in the HAZ; an accumulation of Cu in Al–Si eutectics and around the grain boundaries, including α-Al(Mn,Fe)Si and Al2Cu intermetallics; the presence of some continuous grain boundaries in both the clad and core of the sheet; and the non-uniform precipitation of intermetallics at Al–Si eutectic phases. The impact of these microstructural changes on the corrosion behaviour of the brazed sheet was: to increase the VPD of the re-solidified clad matrix; to introduce localized corrosion susceptibility on the brazed clad and core structures; and to reduce the cathodic protection power of the re-solidified clad material. As a result of the correlation between microstructure and electrochemical behaviour, it was concluded that corrosion resistance of the modified aluminium brazing sheet could be improved by applying a post-braze heat treatment.

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Organic coatings form an effective barrier between metals and their environment, providing them protection against corrosion. Corrosion on coated metals depends mainly on the diffusion of water through the coating, the loss of adhesion at the interface between the coating and the metal (delamination), the rate of the chemical and electrochemical reactions under the coating and the treatment of the metal surface before the coating application. Many aggressive ions are transported toward and inside the coating through water. In organic coatings, typically, the water absorbed by the coating affects the polymer matrix structure, and it causes swelling and stresses, which may result in cracks. Swelling and cracks enhance the transport of water into the solid polymer, and concurrently the diffusion of ions. Over time also, the chemical structure of the polymer may change, adversely affecting its barrier properties and overall performance. In this chapter, we focus on methods to quantify the transport of electrolyte in organic coatings. We mark out the main characteristics, advantages and limitations of each one of them.

The properties of oxide formed on pure aluminium in acetate buffers under controlled potential, temperature, and pH are characterized by in situ electrochemical techniques and spectroscopic visual ellipsometry (VISSE). Monitoring the current density (cd) during transition between different applied potentials gives direct information about Faradaic changes in the oxide properties, while the ellipsometer monitors the changes in the actual thickness and refractive index of the film. Electrochemical impedance spectroscopy (EIS) reveals, in addition to film properties, information about the charge transfer processes and adsorption at steady-state conditions. VISSE and ex situ transmission electron microscopy (TEM) indicate the presence of a two layered oxide structure, consisting of the barrier and a porous hydrated layer. The thickness and density of these two layers are monitored in situ during growth and dissolution. The thickness of the barrier layer depends reversibly on the applied potential, while the thickness of the hydrated layer is less affected by the potential. The absorption sensitive parameter is correlated with the buffer concentration and therefore believed to be related to the acetate.

A Pt microelectrode was used to measure the oxygen consumption by redox reduction (ORR) on electrochemically polarised zinc in the redox competition mode.

No abstract is provided for this article.

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This study presents an innovative sensor-based methodology for the non-destructive, in-situ evaluation of transport properties of protective coatings, as well as detection of onset of corrosion at the coating-metal interface. This technique monitors capacitance changes induced by electrolyte diffusion through the coating. To validate this approach, Odd Random Phase Electrochemical Impedance Spectroscopy (ORP-EIS), as a powerful technique, was employed. In ORP-EIS technique proposed previously by our group, in addition to the effectively shortened measurement time, initial fast water-uptake and its diffusion coefficient can be studied using instantaneous impedance. Results obtained from the sensor-based method demonstrated strong correlation with ORP-EIS data, confirming the reliability and efficacy of the proposed technique. This innovative sensor approach offers a promising tool for in-situ monitoring of coating performance in corrosive environments.

Effective corrosion inhibition of mild steel 1030 at 0.01 M NaCl concentration was achieved by the use of the nontoxic surfactant salt cetrimonium trans-4-hydroxy-cinnamate (CTA-4OHcinn). Polarization analysis on the steel samples immersed for 24 h in the control and CTA-4OHcinn-containing solutions shows the development of a passivation potential that is more obvious at higher inhibitor concentrations along with a maximum inhibition efficiency of 97.8%. Electrochemical impedance spectroscopy (EIS) pinpoints the effect of the inhibitor on the corroding regions of the metal surface, showing an increase in the local electric resistance and conversely a decrease in the local capacitance, which indicates that the charge transfer in the corroding regions is being hindered by a deposition process. This is consistent with scanning electron microscopy (SEM) images, showing the presence of a porous oxide matrix that fills localized corrosion sites on the metal surface after 24 h of immersion in a 0.01 M NaCl + 10 mM inhibitor solution. Additionally, SEM analysis also shows the formation of an organic film surrounding the defects that is able to shield chloride attack. As a result of diffusion of chloride from the defects below the protective film, filiform corrosion can be seen. Time-resolved impedance analysis over the first 120 min of immersion in the control and inhibitor solution shows that significant inhibitor protection does not take place immediately and there is a lag phase in the first 50 min of immersion, suggesting that early localized corrosion drives further adsorption of inhibitor micelles on the metal surface. This is in agreement with X-ray photoelectron spectroscopy (XPS) analysis, which indicates a complete surface coverage over the first 2 h of immersion in a concentrated inhibitor solution. XPS also shows the heterogeneity of the film, where some parts are poorly covered, revealing the underlying surface containing iron.

No abstract is provided for this article.

The feasibility of using Spectroscopic Ellipsometry (SE) for the characterisation of silane films deposited on aluminium substrates is demonstrated in the case of the non-functional bis-1,2-(triethoxysilyl)ethane (BTSE) and bis-functional bis-(3-triethoxysilylpropyl)tetrasulfane (BTESPT) silanes. This method measures the polarisation change of the light due to the interaction with the sample surface. It is called spectroscopic if the measurement is performed at various wavelengths within the spectral range. In this paper, the set up of optical models used to interpret the SE data of both silane/Al systems are presented. A few examples of different applications of SE for silane characterisation are given. Direct evidence of modification in BTSE layer structure, induced by the curing of the silane coated panels is underlined using SE. The effect of Al surface pre-treatments on the thickness and morphology of BTESPT layers is presented. It is also demonstrated that Auger Electron Spectroscopy (AES) can be employed as a complementary technique permitting the validation of the optical results.