The adhesion properties of a FeCrVN experimental tool alloy immersed in pure water and sodium chloride solution have been studied by Quantitative Nanomechanical Property Mapping to understand the influence of microstructure on corrosion initiation of this alloy. The approach used here allows early observation and identification of pre-pitting events that may lead to passivity breakdown of the alloy. Adhesion provides a good distinction between the different regions and we ascribe this to their vanadium and nitrogen contents. Finally, the prepitting is characterized by generation of small particles in specific regions of the surface with low chromium content.

The effect of two concentrations of H2S (0.5 and 2.5 ppm), in controlled laboratory conditions (20 °C, 75%RH), on the atmospheric corrosion of pure Ag, Cu and Ni was investigated in this study. The corrosion product morphology and composition were analysed through a multi-technique approach including SEM/EDX, Raman spectroscopy, XPS and XRD. Different corrosion products were identified depending on the type of characterisations providing a better overview of the effect of H2S on the atmospheric corrosion of pure Ag, Cu and Ni. Possible mechanisms involved in the formation of these corrosion products are also discussed in this work. © 2022 The Authors

Digital Image Correlation (DIC), Acoustic Emission and Electrochemical Noise measurements were applied to study the growth of multiple intergranular cracks as a colony on an Alloy 600 in a tetrathionate solution. Cracks exceeding 55 μm in length and 0.45 μm in opening were successfully detected by DIC. Moreover, crack population was classified into initiating, active and dormant cracks, active population being the larger one. The emergence and intensification of interactions produced a modification on the colony growth behavior. They range from a mostly surface crack propagation (in the absence of interactions), to in depth propagation predominantly governed by crack shielding

The role of Sn on the atmospheric corrosion performance of binary Cu-Sn bronze alloys (4–6 wt.% Sn) compared with Cu metal used in outdoor architecture is elucidated in terms of microstructure, native surface oxide composition, patina evolution, corrosion rates, appearance and metal release. Results are presented for non-exposed surfaces and surfaces exposed at different urban and marine sites in Europe up to 5 years and based on multi-analytical findings from microscopic, spectroscopic, electrochemical and chemical investigations. Alloying influenced the corrosion, aesthetic appearance and patina evolution, differently for urban and marine sites, whereas no effects were observed on the release pattern. © 2019 The Authors

The corrosion resistance of a two-layer polymer (silane+parylene) coating, on implant stainless steel was investigated by microscopic observations and electrochemical measurements. Long term exposure tests in Hanks solution revealed that the coating of 2μm can be successfully used for corrosion protection. However, the addition of H2O2, simulating the inflammatory response of human body environment causes a dramatic destruction of the protective coating. Analysis of the experimental data in terms of circuit models enables proposing a deterioration mechanism. OH ^{radicals formed at the metal surface attack the polymer, thus the deterioration starts from the metal/polymer interface and progress towards the outward surface. © 2010 Elsevier Ltd.}

The influence of surface finishing (polishing and passivation) on the release of Cr, Fe, Ni from the stainless steel 316 implant materials to Hanks solution with or without H2O2 (simulating a body inflammatory response) was investigated. The surfaces were characterized by means of SEM EDXS, XPS and Kelvin Probe measurements before and after exposure to the synthetic body fluids. The total metal ions release rates are more than 10 times higher in the presence of H2O2, independently of the surface finishing. In the absence of H2O2, formation of a surface layer consisting mainly of Ca3(PO4)2 was observed, most likely it was responsible for the observed decrease of the release rates. © 2009 Elsevier Ltd. All rights reserved.

Oxygen pollution in hydrogen sulfide (H2S) saturated test solutions can compromise the results of standardized tests, which guide materials selection in safety-critical components. To examine the temporal evolution of such contamination, we have used the electrochemical methods of impedance spectroscopy and hydrogen permeation to study the corrosion of iron exposed to oxygen-polluted H2S-saturated solutions. EIS analyses were performed with a previously developed model, which explicitly accounts for the contribution of a conductive and porous iron sulfide overlayer. A good correlation is found between corrosion estimates from EIS and weight loss, measured to be higher than the O2-free case. Hydrogen permeation studies across the iron membrane were conducted to qualitatively evaluate the impact of dissolved O2 on hydrogen entry. We observe that O2 contamination was found to significantly reduce hydrogen charging into the metal. 

A corrosion behaviour study of pure phases of zinc and zinc-magnesium (MgZn2) exposed to humid air at 35°C for 4days is presented. For zinc, hydroxide formation at the surface and zinc oxide in the first innerlayers is observed. The corrosion of the MgZn2 leads to the segregation of magnesium at the surface to mainly form magnesium hydroxycarbonate: the presence of magnesium modifies the corrosion products. At larger depths, metallic zinc coexists with magnesium oxide and hydrozincite. The higher reactivity of MgZn2 alloy can be attributed to the interaction with carbonate ions.

We present a corrosion behaviour study of pure phases of zinc and zinc-magnesium contaminated with NaCl and exposed to humid air for 30days: Zn, Mg 2Zn 11 and MgZn 2. The composition of corrosion products is analysed using infrared spectroscopy (FTIR), X-ray diffraction (XRD), ion chromatography (IC), and X-ray photoelectron spectroscopy (XPS). The improved corrosion stability of MgZn 2 is found to be connected to changes in the surface pH and to the nature of the formed corrosion products. The presence of magnesium modifies the proportion of the OH and CO 3 bonds in the corroded products. This explains the improvement in corrosion resistance.

The corrosion behaviour of pure zinc and zinc-magnesium-aluminium alloy (ZMA) has been studied during 6months of exposure in marine environment (Brest, France). The composition of corrosion products is analysed using infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). An improved corrosion resistance of ZMA is observed. This improvement is found to be connected to Mg2+ and Al3+ induced quenching of corrosion activity and to the enhancement of NaZn4Cl(OH)6SO4·6H2O in the formed corrosion product.

In this study, the time-dependent corrosion protection ability of 10-15. μm thin polydimethylsiloxane-nanoparticle composite coatings was evaluated using mainly open circuit potential and electrochemical impedance spectroscopy measurements. The best result was obtained for the coating containing 20. wt% hydrophobic silica nanoparticles, where it was possible to achieve protection for almost 80 days in 3. wt% NaCl solution. The protective properties offered by this coating are suggested to be due to a synergistic effect of the hydrophobicity of the polydimethylsiloxane matrix and the prolonged diffusion path caused by addition of hydrophobic silica particles.

The present investigation highlights corrosion protection of carbon steel by a waterborne acrylate-based matrix coating, with and without reinforcement by cellulose nanocrystals, by using electrochemical impedance spectroscopy in 0.1 M NaCl solution over a period of 35 days. Interactions between cellulose nanocrystals and the matrix coating were demonstrated by Fourier transform infrared spectroscopy. The results show that both coatings have high barrier performance but different protective characteristics during long-term exposure. The differences can be attributed to the reinforcement effect of cellulose nanocrystals caused by hydrogen bonding interactions between cellulose nanocrystals and the matrix coating.

Scanning Kelvin Probe was applied to study passivation of AISI 304L stainless steel after cathodic polarisation. The rate of passivation in air decreased as a function of duration and current density. X-ray Photoelectron Spectroscopy showed enrichment of the surface film by hydroxides of Fe (II) that was the result of hydrogen effusion from the bulk. SKP measured a decreased potential drop in the passive film. Pre-polarisation accelerates the crevice corrosion of steel in presence of chlorides. Using SKP mapping, increased hydrogen sub-surface concentration and lower level of passivity was observed in anodic zones of the crevice.

Even though magnesium, as a structure metal, is most commonly used in an atmospheric environment, most investigations of magnesium are performed in solution. In the present work the atmospheric corrosion of two commonly used magnesium alloys, AZ91D and AM50, has been investigated from the initial stages up to the most severe forms of corrosion. A detailed investigation of the morphology of a corrosion attack and its development over time shows that the atmospheric corrosion mechanism is similar for the two alloys. Based on these findings a schematic model of the initial atmospheric corrosion attack on AZ91D is presented and discussed. © 2009 Elsevier Ltd. All rights reserved.

Magnesium alloy AZ91D was exposed in humid air at 95% relative humidity (RH) with a deposition of 70 μg/cm-2 NaCl. The corrosion products formed and the surface electrolyte were analysed after different exposure times using ex situ and in situ FTIR spectroscopy, X-ray diffraction and Ion Chromatography. The results show that magnesium carbonates are the main solid corrosion products formed under these conditions. The corrosion products identified were the magnesium carbonates hydromagnesite (Mg5 (CO3)4 (OH)24H2O) and nesquehonite (MgCO3 3H2O). The corrosion attack starts with the formation of magnesite at locations with higher NaCl contents. At 95% RH, a sequence of reactions was observed with the initial formation of magnesite, which transformed into nesquehonite after 2-3 days. Long exposures result in the formation of pits containing brucite (Mg(OH2)) covered with hydromagnesite crusts. The hydromagnesite crusts restrict the transport of CO2 and O2 to the magnesium surface and thereby favour the formation of brucite. Analysis of the surface electrolyte showed that the NaCl applied on the surface at the beginning was essentially preserved during the initial corrosion process. Since the applied salt was not bound in sparingly soluble corrosion products a layer of NaCl electrolyte was present on the surface during the whole exposure. Thus, Na+ and Cl- ions can participate in the corrosion process during the whole time and the availability of these species will not restrict the atmospheric corrosion of AZ91D under these conditions. It is suggested that the corrosion behaviour of AZ91D is rather controlled by factors related to the microstructure of the alloy and formation of solid carbonate containing corrosion products blocking active corrosion sites on the surface.

β-Mg17Al12, η-Al8Mn5 and an α-magnesium phase have been synthesized from pure components by controlled solidification procedures. These phases have been studied using different electrochemical techniques including the scanning Kelvin probe (SKP). From the results, it was possible to determine the nobility and the rate of the cathodic reaction of the different phases. Measurements have also been made on an AZ91D Mg-alloy using scanning Kelvin probe force microscopy (SKPFM) and field emission gun scanning electron microscopy (FEG-SEM). The results show that the Volta potentials measured with the scanning Kelvin probe (SKP) on bulk intermetallics are comparable with those recorded with the SKPFM on the AZ91D alloy. It is shown that SKPFM provides information on the local nobility of the different intermetallic particles and phases on the submicron scale. Both the η-Al8Mn5 phase and the β-Mg17Al12 phase in AZ91D showed a more noble potential than the α-magnesium phase. It is also shown that the aluminium-rich coring along the grain boundaries results in measurable changes in the Volta potential. Finally, the role of the β-Mg17Al12 phase and the η-Al8Mn5 phase in the corrosion behaviour of AZ91D is discussed in term of local nobility, surface coverage of the cathode and the cathodic activity of the different phases.

Corrosion properties of aluminum alloy AA6063-T5 were investigated in molybdate-containing NaCl solutions. Electrochemical, microscopic, and spectroscopic experiments were utilized to examine the mechanism of corrosion inhibition by molybdates. SEM-EDX, magnetic force, and intermodulation electrostatic force microscopy data suggested that the inhibition initiation preferentially occurred over Fe-rich cathodic IMPs. Spectroscopic measurements demonstrated that the formed surface layer consists of mixed Mo(VI, V, IV) species. This layer provided inhibition with an efficiency of ∼90% after 4 h of exposure. High efficacy of ∼70% was achieved even after one week of exposure. A two-step oxidation-reduction mechanism of corrosion inhibition by aqueous molybdates was proposed. © 2020 The Authors

Corrosion and corrosion inhibition of WE43 magnesium alloy were investigated in NaCl solutions containing different amounts of sodium molybdate. Electrochemical, microscopic, and spectroscopic experiments were utilized to examine the mechanism of corrosion inhibition by molybdates. Electrochemical data showed that Na2MoO4 inhibitor provides reliable inhibition at concentrations at and above 100 mM. Raman and XPS spectroscopy demonstrated that the formed surface layer consists of mixed Mo(V, IV) species. This layer provided inhibition with an efficiency of 91–99 % after 24 h of exposure. A two-step oxidation-reduction mechanism of corrosion inhibition of the WE43 alloy by aqueous molybdates was proposed. © 2021 The Author(s)

Chemical interactions between aqueous vanadium species and aluminium alloy AA6063-T5 were investigated in vanadate-containing NaCl solutions. Confocal Raman and X-ray photoelectron spectroscopy experiments were utilised to gain insight into the mechanism of corrosion inhibition by vanadates. A greenish-grey coloured surface layer, consisting of V+4 and V+5 polymerized species, was seen to form on the alloy surface, especially on top of cathodic micrometre-sized IMPs, whereby suppressing oxygen reduction kinetics. The results suggest a two-step mechanism of corrosion inhibition in which V+5 species are first reduced to V+4 or V+3 species above cathodic IMPs, and then oxidized to mixed-valence V+5/V+4 polymerized compounds. 

The atmospheric corrosion of line hot dip ZnMgAl coating was investigated at low and ambient concentration of CO2 as a function surface chloride concentration and temperature and compared to conventional hot dip galvanised (GI) and Galfan coatings. The corrosion of zinc coatings was enhanced in low CO2 conditions and ZnMgAl material was more affected than GI, and in the range of the Galfan coating. An obvious pH effect was underlined in low CO2 conditions. Layered double hydroxide (LDH) and simonkolleite were mainly formed on ZnMgAl coating in the absence of CO2 while hydroxycarbonate and simonkolleite were dominating in ambient air.

The study aimed at developing a test method allowing to evaluate the critical pitting temperature of corrosion resistant alloys in H2S containing environments. ASTM G150 method is indeed not appropriate in sour environment due to the oxidation of H2S at high applied potential and to the decrease of H2S partial pressure as the temperature increases. The study underlines that critical pitting temperature measurement is possible in H2S-containing environments but that the determined temperature is probably not potential independent. The methodology can however be used to rank different alloys provided the selection of a test media representative from service conditions.

Commercial Oxsilan, 3-aminopropyltriethoxysilane and sol-gel siloxane coatings were applied on AA6016 aluminium alloy before electrocoating. Standard filiform corrosion test demonstrated the pre-treatment role on the under-paint corrosion rate. All pre-treatments increase the coating adhesion in water electrolyte (EIS). Anodic undermining is the mechanism of the coatings de-adhesion (SKP). Electromotive force (difference in potentials of defect-surrounding interface) and interface ability to promote the chloride migration are rate-determining factors of the filiform corrosion. Contrary to other pre-treatments, the aminosiloxane decreases the interfacial potential, facilitates the chlorides migration and leads to anodic de-adhesion of large coated areas (Tof-SIMS and EDXS).

Scanning Kelvin probe (SKP) can be applied for mapping of subsurface hydrogen in steels. The good spatial resolution is combined with poor quantification. Controversy, the electrochemical permeation technique (EPT) is extremely sensitive to hydrogen flux but has low spatial resolution. Thus, a local hydrogen quantification method using SKP measurements calibrated by EPT was developed. The fixed amount of hydrogen flux in mild steel membrane was obtained by cathodic polarization and was detected using the two methods. A semi-logarithmic relationship between SKP potential drop and the hydrogen sub-surface concentration underneath of the corroding surface was established. SKP quantification was applied for mapping the subsurface hydrogen in steel corroding under various atmospheric corrosion conditions. 

The initial atmospheric corrosion of ZnAl2Mg2 coated steel in humid air with 80ppb SO2 was studied using in situ Infrared Reflection Absorption Spectroscopy, XRD and SEM. Corrosion products formed in SO2- and SO2 and NaCl containing environments on ZnAl2Mg2 (ZM) were dominated by Mg-containing sulphite and sulphates with sulphite formed mainly initially. The sulphite formation is connected with dissolution of the Mg-containing oxide layer present initially. This is followed by a localised corrosion process where Mg rich phase in the binary eutectic microstructure is dissolved anodically while the Zn-rich phase is the site for the cathodic oxygen reduction.

The formation of corrosion products on Zn55Al coated steel has been investigated upon field exposures in a marine environment. The corrosion products consisted mainly of zinc aluminium hydroxy carbonate, Zn0.71Al0.29(OH)2(CO3)0.145·xH2O, zinc chloro sulfate (NaZn4(SO4)Cl(OH)6·6H2O), zinc hydroxy chloride, Zn5(OH)8Cl2·H2O and zinc hydroxy carbonate, Zn5(OH)6(CO3)2 were the first three phases were formed initially while zinc hydroxy carbonate Zn5(OH)6(CO3)2 was formed after prolonged exposure in more corrosive conditions. The initial corrosion product formation was due to selective corrosion of the zinc rich interdendritic areas of the coating resulting in a mixture of zinc and zinc aluminium corrosion products. © 2010 Elsevier Ltd.

NaCl induced atmospheric corrosion of ZnAl2Mg2 coated, electrogalvanised (EG) and hot dipped galvanised (HDG) steel was studied using in situ infrared reflection absorption spectroscopy, XRD and SEM. Initial corrosion leads to the formation of Mg/Al and Zn/Al layered double hydroxides (LDHs) on ZnAl2Mg2, due to the anodic dissolution of Zn-MgZn2 phases and cathodic oxygen reduction on Zn-Al-MgZn2, Al-phases and on zinc dendrites. In contrast to EG and HDG, were no ZnO and Zn5(OH)8Cl2{dot operator}H2O detected. This is explained by the buffering effect of Mg and Al which inhibit the ZnO formation, reduce the cathodic reaction and corrosion rate on ZnAl2Mg2.

The atmospheric corrosion of hot dipped galvanized steel was studied in a wide-world exposure in Europe, East Asia and USA. The corrosion product composition, morphology and surface distribution was investigated after 0.5, 1 and 2 years exposure. The corrosion was localized for all exposure conditions with sulfate and chloride containing corrosion products(Zn(OH)2)3·ZnSO4·nH2O,NaZn4(SO4)(OH)6Cl·6H2O and Zn5(OH)8Cl2·H2O formed at the anodic sites in corrosion pits and Zn5(OH)6(CO3)2 mainly in the outer parts of the corrosion products and cathodic areas outside the pits. The content of the sulfate containing corrosion products increased in the order marine<marine/urban, marine/industrial<industrial/urban.

Ti6Al4V surfaces were exposed to simulated inflammation conditions in H2O2-containing phosphate buffered saline with and without FeCl3. Scanning electron microscopy analysis revealed significantly different degradation modes for the α and β phases. While the α grains are covered by a ca. 400 nm thick protective nanostructured oxide layer, the attack of the β phase generates a porous microstructure with microscaled cracks and a low polarization resistance. The β phase is postulated to be sensitive to H2O2 reduction products and less able to generate a passive oxide film. The presence of FeCl3 enhances the cathodic activity and the β phase degradation.

Zn-5Al and Zn-3Al-2Mg model alloys were cast and heat treated in order to obtain specimens with distinct microstructures and identical chemical compositions. The microstructure was characterised in detail to identify composition, size and distribution of present phases. Mass losses of samples with different microstructures and identical chemical compositions that were subjected to a cyclic corrosion test and a test under non-rinsing conditions differed by a factor of up to two. The mechanism is discussed based on measurements of corrosion stability of individual phases and chemical and phase compositions of corrosion products.

Recently, superior corrosion properties of zinc coatings alloyed with magnesium have been reported. Corrosion behaviour of model zinc-magnesium alloys was studied to understand better the protective mechanism of magnesium in zinc. Alloys containing from 1 to 32 wt.% magnesium, pure zinc, and pure magnesium were contaminated with sodium chloride and exposed to humid air for 28 days. Composition of corrosion products was analyzed using infrared spectroscopy (FTIR), ion chromatography (IC), and Auger electron spectroscopy (AES). The exposure tests were completed with scanning Kelvin probe (SKP) and electrochemical measurements. Weight loss of ZnMg alloys with 1-16 wt.% magnesium was lower than that of pure zinc. Up to 10-fold drop in weight loss was found for materials with 4-8 wt.% Mg in the structure. The improved corrosion stability of ZnMg alloys was connected to the presence of an Mg-based film adjacent to the metal surface. It ensured stable passivity in chloride environment and limited the efficiency of oxygen reduction.

The tendency of coil-coated hot dip galvanized materials to blistering was investigated in accelerated tests and by electrochemical impedance spectroscopy. The best prediction of outdoor performance at a marine test site was obtained in the Q-panel condensation test (QCT) at 60 °C with the minimum testing time of 500. h. The ratio of the impedance modulus at 60 and 25 °C measured at a low frequency of 0.1. Hz correlated with the extent of blistering after outdoor exposures and accelerated tests. It is proposed that this parameter reflects the interaction of the polymer and the metal/polymer interface with water.

Formation of corrosion products on hot-dip galvanised steel. (HDG), Zn-5Al, Zn-11Al-3Mg-0.2Si, Zn-16Mg and Zn-1.5Al-1.5Mg with pre-deposited NaCl was followed in humid air at 20. °C. The alloyed coatings showed an improvement in mass loss by a factor of 4-7 to HDG. Corrosion products on the alloyed coatings contained twice as much carbonates than those formed on HDG. Magnesium dissolved preferentially, and aluminium-enriched phases were the most stable. Magnesium buffered the pH at cathodic sites, thus hindering the formation of zinc oxide and inhibiting the oxygen reduction. Magnesium products at the metal/corrosion product interface might also have an inhibiting effect.

The corrosion rate of copper and bronze Cu-8. wt.%Sn increased rapidly when the concentration of formic or acetic acid in air reached about 300. ppb at 80% relative humidity (RH) and a temperature of 20. °C. It decreased slowly during the several days after pollutant removal due to the slow rate of pollutant desorption from the metal surfaces. Corrosion of these metals was barely affected by the acids at RH up to 60%. For iron, the critical concentration of formic acid in air which led to surface activation at 80% RH was between 1000 and 1590. ppb.

The effect of sodium, calcium, and magnesium chlorides deposited on zinc and carbon steel surfaces was studied under atmospheric conditions. The cations strongly affected the corrosion rate of zinc, whereas they had a significantly lower impact on the corrosion of carbon steel. The corrosivity of cations of chloride salts for zinc increased in order of Mg2+ < Ca2+ < Na+. The higher corrosion resistance of zinc treated with calcium and magnesium chlorides was connected to prevention of formation of hydrozincite during zinc exposure in wet air. It was observed that zinc weight loss and the carbonate to simonkolleite ratio in corrosion products were correlating. The principal protective effect of bivalent cations can be seen in the decrease of pH of the surface electrolyte, which was caused by hydrolysis of such cations and subsequent formation of simonkolleite that blocked the cathodic sites.

Microstructure influence on corrosion behavior of an N-based tool alloy (Fe-Cr-V-N) has been studied. Electron microscopy analysis showed two types of hard phases in the alloy. One-pass mode scanning Kelvin force microscopy (KFM) was used to investigate relative nobility of the hard phases. Volta potential mapping indicates higher nobility for the hard phases than the alloy matrix, and, the V- and N-rich particles exhibit the highest Volta potential. Post-polarization analysis by SEM revealed localized dissolution initiated in matrix regions adjacent to hard phase particles, and the boundary region surrounding the Cr- and Mo-rich particles is more prone to localized corrosion.

Influence of a few percents additives of polyaniline doped with phosphoric acid (PAni-PA) and ceria nanoparticle on corrosion protection of a new ultraviolet (UV)-cure polyester acrylate coating have been studied for coil coating on carbon steel by electrochemical measurements during exposure to a NaCl solution. The results demonstrate that the presence of ceria nanoparticles improves the barrier property and stability of the coating. Adding the PAni-PA results in active corrosion protection for carbon steel due to passivation of the steel, and the combination of both additives greatly enhances the protection property over that of the coating matrix alone.

The relative nobility of Cr2N in duplex stainless steels (DSSs) was investigated in isothermally aged 2205 and 2507 DSSs using scanning Kelvin probe force microscopy (SKPFM) and SEM/EDS. The specimens contained nitrides, austenite and sigma phase but no ferrite. In these materials, Cr2N exhibits a higher Volta potential than sigma phase and austenite, implying the highest practical nobility of Cr2N compare to the surrounding phases. The composition and alloying effect can explain the relative nobility of the phases. The apparent "size effect" of small Cr2N on the measured Volta potential difference is probably due to the influence of surrounding matrix. © 2009 Elsevier Ltd. All rights reserved.

Modelling and prediction of the copper concentration released from copper plumbing tubes due to corrosion, dissolution, precipitation and other processes has not previously been successful. The model presented here is based on a set of dissolution and precipitation reactions, equilibrium between species in solution and solids, mass balance, kinetic expressions, adsorption isotherms, and surface area coverage by precipitates.The model developed has created two major outputs: first; it is the most conclusive collection of mechanistic considerations to date; and second; reasonable correlations between the model and actual data have been obtained for a broad range of waters. © 2012 Elsevier Ltd.

The atmospheric corrosion of zinc aluminium magnesium (ZnAlMg) coated steel was studied in a worldwide exposure in Europe, East Asia and USA. The mass loss of ZnAlMg coated steel was about 2–3 times lower compared to hot dipped galvanised steel (HDG) after 4 years exposure. The corrosion of ZnAlMg coated steel was highly localised with selective corrosion attacks in the eutectic phases of the coating. Sulfate and chloride containing corrosion products were formed in the corrosion pits while zinc hydroxy carbonate and carbonate containing layered doubly hydroxides (LDH) formed mainly in the outer parts of corrosion attacks.

The deliquescence of the corrosion species produced by nuclear waste incineration, in particular ZnCl2, makes wet corrosion possible even in dehumidified atmosphere complicating the corrosion risk management of the equipment. A specific cyclic corrosion test was used to assess the compatibility of corrosion resistance alloys to such conditions. Thereby, AISI 316 L welds resisted somehow to pitting but experienced severe stress corrosion cracking, while UR66™ showed only pitting in the heat affected zone. Hastelloy® C22 exhibited better performance, with localized corrosion only in the fusion zone, that was greatly influenced by the composition of the filler materials and welding techniques.

Hydrogen permeation through high strength DP1180 steel was studied by Scanning Kelvin Probe (SKP) and X-ray photoelectron spectroscopy (XPS). The XPS analyses showed that hydrogen desorption from the steel increased the ratio Fe(II)/Fe(III) related to oxide film reduction. In parallel, a drop of the electrochemical potential in the oxide film was measured by SKP. Analyses of the composition and potential of the surface were correlated based on Nernst red-ox thermodynamic equilibrium. From this approach, it was shown that the SKP potential can be a measure of hydrogen affecting the surface oxide, but additional contributions should be considered. © 2022 The Authors

This paper presents new findings about the passive film formed on super duplex stainless steel in ambient air and corrosive environments, studied by synchrotron grazing-incidence X-ray diffraction (GIXRD). The passive film, formed in air, was seen to be a nano-crystalline mixed-oxide. Electrochemical polarisation to the passive region in aqueous 1 M NaCl at room temperature resulted in an increase of the passive film thickness, preferential dissolution of Fe, and partial loss of crystallinity. After termination of polarization to the transpassive regime, reformation of the mixed-oxides was observed, showing a thicker, semi-crystalline, and more defective nature (more vacancies) with further new oxides/hydroxides.