Three complementary experimental techniques for in situ surface analysis have been combined for the first time in order to explore the chemistry and physics of a copper surface exposed to humidified air. Infrared reflection absorption spectroscopy, quartz crystal microbalance and atomic force microscopy provide a congruent picture of the processes occurring at the surface. At a given relative humidity, cuprous oxide forms according to an approximately logarithmic rate law. In addition, an aqueous adlayer of constant mass physisorbs on the surface. Increased relative humidity stimulates the physisorption of water and enhances the nucleation rate of oxide grains, thereby increasing the formation rate of cuprous oxide.

Good high-temperature corrosion resistance of Fe-Al alloys in oxidizing environments is due to the alpha-Al2O3 film which is formed on the surface provided temperature is above 900 degrees C and the Al-content of the alloy exceeds the critical value. Ab initio calculations combined with experiments on Fe-13Al, Fe-18Al, Fe-23Al and Fe-10Cr-10Al alloys show that the beneficial effect of Cr on the oxidation resistance is significantly related to bulk effects. The comparison of experimental and calculated results indicates a clear correlation between the Fe-Cr chemical potential difference and the formation of the protective oxide scales. (C) 2010 Elsevier Ltd. All rights reserved.

Good high-temperature corrosion resistance of Fe-Al alloys in oxidizing environments is due to the alpha-Al2O3 film which is formed on the surface provided temperature is above 900 degrees C and the Al-content of the alloy exceeds the critical value. Ab initio calculations combined with experiments on Fe-13Al, Fe-18Al, Fe-23Al and Fe-10Cr-10Al alloys show that the beneficial effect of Cr on the oxidation resistance is significantly related to bulk effects. The comparison of experimental and calculated results indicates a clear correlation between the Fe-Cr chemical potential difference and the formation of the protective oxide scales.

Hot corrosion behavior of solution precursor plasma spray (SPPS) thermal barrier coating (TBC) in molten salt mixtures of 90wt.% Na<inf>2</inf>SO<inf>4</inf>+5wt.% V<inf>2</inf>O<inf>5</inf>+5wt.% NaCl and 50wt.% Na<inf>2</inf>SO<inf>4</inf>+50wt.% V<inf>2</inf>O<inf>5</inf> at 900°C is compared vis-à-vis atmospheric plasma spray (APS) coating. APS TBCs show better hot corrosion resistance than SPPS TBCs in both the salt mixtures. The vertical cracks in SPPS coatings, meant for strain tolerance and high thermal cycling life, serve as channels for transporting salts across the coating to bond coat/top coat interface and accelerate failure. © 2015 Elsevier Ltd.

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 resistance to environment-assisted cracking (EAC) of AISI 420 martensitic stainless steel (MSS) was investigated in 0.3 M NaCl solution (room temperature) at constant loads for 30 days. The steel tempered at 250 degrees C was superior to the 500 degrees C-temper, which showed corrosion pits favouring cracking. The fracture surface showed faceted grains, cleavage, striations, and inter- and transgranular cracks, suggesting a mixed stress corrosion cracking (SCC) and hydrogen embrittlement (HE) mechanism as the cause for EAC. Finite element modelling (FEM) indicated strain/stress localization at the mouth of deep pits and at the wall of shallow pits, displaying the favoured locations for pit-to-crack transition.

The hot corrosion behaviour of wire-arc additive manufactured and wrought ATI 718Plus® are studied. ATI 718Plus® produced by the additive manufacturing process, in the as-processed condition, exhibits a significantly lower hot corrosion resistance in comparison to the wrought alloy. Analytical electron microscopy and spectroscopy techniques, with corroboration by thermodynamic calculations, are used to identify the underlying cause of the poor hot corrosion resistance. Based on the understanding accrued from the analyses, post-processing heat treatments are used to improve the hot corrosion resistance, which is valuably pertinent to the application of ATI 718Plus® produced by additive manufacturing in hot corrosive environments. © 2019 Elsevier Ltd

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

NbSi2 monoliths were prepared by self-propagating high temperature synthesis (SHS) and hot pressing (HP) and their oxidation behavior was investigated at various temperatures (823 K to 1123 K) in air. The combustion mode of SHS reaction was steady state combustion, and the combustion product was single-phase NbSi2. Oxidation studies show that the highest mass gain was 0.95675 kg m-2 at 1023 K. In cyclic oxidation, the oxidation rate was reduced and the mass gain was only 0.15507 kg m-2. A dense protective amorphous SiO2 scale formed at 823 K and 923 K whereas a porous multilayer SiO2 and α/β-Nb2O5 oxide scales formed at and above 1023 K and spalled off. Pest oxidation of NbSi2 monoliths was not observed in hot pressed NbSi2 monoliths

NbSi2 monoliths were prepared by self-propagating high temperature synthesis (SHS) and hot pressing (HP) and their oxidation behavior was investigated at various temperatures (823-1123 K) in air. The combustion mode of SHS reaction was steady state combustion, and the combustion product was single-phase NbSi2. Oxidation studies show that the highest mass gain was 0.95675 kg m(-2) at 1023 K. In cyclic oxidation, the oxidation rate was reduced and the mass gain was only 0.15507 kg m(-2). A dense protective amorphous SiO2 scale formed at 823 K and 923 K whereas a porous multilayer SiO2 and alpha/beta-Nb2O5 oxide scales formed at and above 1023 K and spalled off. Pest oxidation of NbSi2 monoliths was not observed in hot pressed NbSi2 monoliths.

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 formation of α’ martensite at the surface of an AISI 304 stainless steel subjected to cyclic heating in humidified air is reported. The α’ martensite formed during the cooling part of the cyclic tests due to local depletion of Cr and Mn and transformed back to austenite when the temperature again rose to 650 °C. The size of the α’ martensite region increased with increasing number of cycles. Thermodynamical simulations were used as basis for discussing the formation of α’ martensite. The effect of the α’ martensite on corrosion is also discussed.

In this work, a novel in-situ grown layered double hydroxide (LDH) film co-intercalated with inhibitors (vanadates) and low surface energy substance (laurates) was immobilized on Al substrates. A long-term monitoring of electrochemical impedance spectra (EIS) of the various samples in 3.5 wt.% NaCl solution demonstrated the synergetic protection of the intercalated two functional species. Meanwhile, the X-ray diffraction (XRD) result of the samples after immersion in NaCl solution for a long time presented the anion-exchange process between vanadates/laurates and chlorides. The synergetic effect of the two species loaded film significantly contributed to the enhanced long-term corrosion protection of aluminum.

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 interplay between atmospheric corrosion and antimicrobial efficiency of bare Cu and Cu5Zn5Al1Sn was studied upon exposures simulating high-touch surface conditions. The survival of the bacteria Bacillus subtilis during surface contact with Cu and Cu5Zn5Al1Sn was examined under different degrees of surface oxidation, tarnishing, wettability and copper ion release. Depending on surface conditions complete bacteria inhibition was obtained within 4 min on Cu and within 6-10 min on Cu5Zn5Al1Sn. The antibacterial efficiency increases slightly with copper release rate and is governed by complex interactions between the corroded metal surface, bacteria and extracellular polymeric substances produced by the bacteria.

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.

The influence of chloride deposition on the formation, evolution and barrier properties of the patina formed on CuSZn5Al1Sn used for architectural cladding is explored via long-term marine field exposures and laboratory investigations. The presence of Cu2O, ZnO, Al2O3 and SnO2 within the inner part of the patina and intercalation of SnO2, Zn-5(CO3)(2)(OH)(6), Zn6Al2(OH)(16)CO3 center dot 4H(2)O, Zn-5(OH)(8)Cl-2 center dot H2O within its outer part, predominantly composed of Cu-2(OH)(3)Cl, significantly reduce the chloride-induced corrosion compared with Cu metal. The intercalation of zinc-rich corrosion products within the patina and not at the top-surface explain their marginal influence on the runoff process that mainly occurs at the outmost surface.

The effect of blue light on atmospheric corrosion of Cu and on the antimicrobial properties was explored upon exposure mimicking the condition of hygienic surface disinfection. The results show that blue light illumination enhanced the formation of Cu2O, resulting in a slightly increased corrosion resistance of Cu without pre-deposited NaCl, whereas the enhanced formation of Cu2O, CuCl and/or Cu(OH)3Cl on copper with pre-deposited NaCl caused concomitant corrosion product flaking and a reduced corrosion resistance. The blue light induced enhancement of Cu corrosion led to increased surface roughness and more pronounced integration of bacteria within the corrosion products.

The complex stratified patina formed on Sn-bronze in chloride-rich atmospheres has been explored through long-term field exposures and short-term laboratory investigations using a multi-analytical approach. The stratified patina is composed of Cu2O- and Cu-2(OH)(3)Cl-rich sublayers intercalated by Sn-oxides, mainly SnO2. The stratification is triggered by events of high chloride deposition, resulting in repeated dissolution and solidification of sublayers, whereby redox reactions between the intermediate products of Sn- and Cu-chlorides play a crucial role. Sn-induced patina stratification is a major reason for enhanced patina flaking on Sn-bronze and its accelerated corrosion rate compared to Cu metal in marine environments.

The golden alloy Cu-5Zn-5Al-1Sn has found many applications because of its appearance and resistance to tarnishing. The microstructure and multi-component surface oxide of Cu-5Zn-5Al-1Sn have been investigated through a multi-analytical approach. Compared to commercial Cu metal, Cu-5Zn-5Al-1Sn has significantly smaller grains and higher fraction of coherent twin boundaries. The 5-10 nm thick oxide formed after diamond polishing has four identified sub-oxides all contributing to the overall corrosion resistance. Cu2O is mainly located in the outer part, followed by ZnO, SnO2 and Al2O3 closer to the alloy substrate. The latter three possess barrier properties, while Cu2O exhibits a more complex structure.

The pitting potential, intrinsic surface acidity, point of zero charge of passive film on Al are studied using first-principles calculations to establish their relationships. Influences of alloying elements Zn, Cr, Nb, Si, Mo and Sc on adsorption of NH3 and NaCl, pHpzc of Al2O3 and pitting susceptibility of Al are investigated. The efficiency for enhancing pitting resistance of Al is evaluated, yielding the ratios Si: Zn: Cr: Mo: Nb: Sc = 1.8: − 0.3: 1: 1.9: 1.4: 0.2. A model for the dependence of pitting potential on the concentration of alloying elements in Al alloy matrix is developed, based on effects of alloying elements on the surface charge of passive film. The effects of Sc on pitting potential and pHpzc of Al oxide are predicted based on the calculated results, which are supported by electrochemical measurement, XPS analysis and contact angle titration.

Potential drop at the oxide film/solution interface plays a critical part in numerous electrochemical processes, especially for the passivated metal-electrolyte system, affecting the passive film breakdown and the pitting initiation. There are still some controversies over the dependence of potential drop at the passive film/solution interface (φf/s) on potential and pH of electrolyte. Herein, we develop a model presenting the linear dependence of φf/s on both potential and pH, as represented by φf/s=φf/s(V=0,pH=0)0+αV+βpH. By analyzing the surface charge (i.e., point of zero charge, pHpzc) and performing first-principles calculations, we provide the insights into the effect of potential and pH on the φf/s, and into the linear relation between φf/s with pH beyond the Nernst relation that is attributed to the role of point defects in pHpzc of passive film on iron. In addition, two methods, e.g., a combination of Mott-Schottky measurement with first-principles, contact angle titration, are suggested to determine the values of α, β and φf/s(V=0,pH=0)0, respectively. The study of passivity of iron in borate buffer solutions validates our model.

Initial corrosion and secondary spreading effects during NaCl particle induced corrosion on zinc was explored using in situ and ex situ FTIR microspectroscopy, optical microscopy, and SEM/EDAX. The secondary spreading effect which occurs upon introduction of humid air on NaCl deposited zinc surfaces was strongly dependent on the CO₂ and SO₂ content of the introduced air. Ambient level of CO₂ (350 ppm) resulted in a relatively low spreading effect, whereas the lower level of CO₂ (<5 ppm) caused a much faster spreading over a larger area. In the presence of SO₂, the secondary spreading effect was absent which could limit the cathodic process in this case. At <5 ppm CO₂, the corrosion is more localized, with the formation of simonkolleite (Zn₅(OH)₈Cl₂ · H₂O), zincite (ZnO) and sodium carbonate (Na₂CO₃), and a larger effective cathodic area. At 350 ppm CO₂, the corrosion is more general and formation of simonkolleite, hydrozincite (Zn₅(OH)₆(CO₃)₂) and sodium carbonate was observed. Sodium carbonate was mainly formed in more alkaline areas, in the inner edge of the electrolyte droplet and in the secondary spreading area. Oxidation of sulphur and concomitant sulphate formation was enhanced in the presence of NaCl particles, due to the formation of a droplet, the separation of the anodic and cathodic areas and the accompanying differences in chemical composition and pH in the surface electrolyte.

A new strategy was proposed to prepare a composite film using mussel adhesive protein Mefp-1 and graphene to achieve corrosion protection and surface lubrication on carbon steel. The dispersibility of graphene in Mefp-1 solution was firstly investigated and deposition methods of Mefp-1/graphene film were proposed. In-situ confocal Raman micro-spectroscopy and electrochemical impedance spectroscopy measurements were utilized to study the corrosion inhibition effect in NaCl solution. Friction tests were conducted to study the tribological properties. Results show that the Mefp-1/graphene film exhibits strong adhesion to carbon steel, provides improved corrosion- and wear-resistance, and a significantly increased lubricity on carbon steel.

This paper focuses on the study of micro-galvanic corrosion of the Cu/Ru couple in KIO4 solution. Practical nobility across the Cu/Ru interface was evaluated by Volta potential mapping, and the morphological changes were monitored by in-situ atomic force microscopy measurements during exposure in a KIO4 solution. Chemical composition of precipitated corrosion product was analyzed by Confocal Raman spectroscopy immediately after the exposure. The results show that Cu is the anode of the Cu/Ru couple, and accelerated dissolution of Cu preferentially occurs near the Cu/Ru interface. However, subsequent formation of insoluble Cu(IO3)2·nH2O leads to precipitation, which impedes further Cu corrosion.

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 2 mu m 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.

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.

Oxidation of the Ni-based superalloy RR1000 has been undertaken in air over the temperature range 600-900 degrees C for times up to 5000 h. The surface oxide consisted of a protective Ti-doped chromia layer but with rutile forming on its outer surface. Sub-surface oxidation of Al and Ti also occurred. The thickening kinetics of the chromia layer were sub-parabolic with initial rates around two orders of magnitude higher than expected for Ti-free chromia. This enhancement and the sub-parabolic kinetics are accounted for by Ti-doping of the chromia layer. Over time the enhancement reduced because of Ti-depletion in the alloy.

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.

Samples of At, Cr, Ni, and Zr were sputter-coated with porous Pt-films with a particle size of 20-30 nm. Thermal oxidation of these samples was studied by gas phase analysis (GPA) and secondary ion mass spectrometry (SIMS). SIMS analysis on partly Pt-coated samples of At, Cr, Ni, and Zr at different oxide depths in areas with Pt and in areas away from Pt indicates an enhanced inward oxide growth in the Pt area and mm-ranged distance from Pt-area. Weight gain measurements on Pt-coated Ni samples show a reduced or increased oxidation rate depending on the amount of porous Pt-coating. Pt has two effects on the thermal oxidation of metals and the overall effect of Pt on the oxidation of metals depends on the mechanism of oxide growth in the absence of Pt.

We systematically study the oxidation properties of sputter-deposited TiB2.5 coatings up to 700 °C. Oxide-scale thickness dox increases linearly with time ta for 300, 400, 500, and 700 °C, while an oxidation-protective behavior occurs with dox=250∙ta0.2 at 600 °C. Oxide-layer’s structure changes from amorphous to rutile/anatase-TiO2 at temperatures ≥ 500 °C. Abnormally low oxidation rate at 600 °C is attributed to a highly dense columnar TiO2-sublayer growing near oxide/film interface with a top-amorphous thin layer, suppressing oxygen diffusion. A model is proposed to explain the oxide-scale evolution at 600 °C. Decreasing heating rate to 1.0 °C/min plays a noticeable role in the TiB2.5 oxidation.

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.

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.

Selective dissolution of duplex stainless steel 2205 in acidic chloride solutions was studied in situ by electrochemical scanning tunnelling microscopy (STM). In 0.05 M H2SO4 + 1 M NaCl, no appreciable active dissolution was observed by in situ STM imaging at the corrosion potential (E-corr), but at potentials higher than E-corr + 1000 mV some selective dissolution at the austenite-ferrite boundary region occurred. In 4 M H2SO4 + 1 M HCl, STM images revealed active dissolution of ferrite grains at around E-corr + 50 mV. Dissolution of austenite grains started to occur at around E-corr + 150 mV, exhibiting steps of submicron scale on the edges.

Passive films were compared on two stainless steels: the recent lean duplex EN 1.4162 and EN 1.4432 (316L). For alloys with significant amount of manganese and nickel, the Mn 2p(3/2) peak will overlap with the Ni-LMM. To resolve this overlap, Ni 2p(3/2) to Ni-LMM intensity ratios were recorded on 1.4432, compensated for overlayer thickness, and then used to fix the Ni-LMM intensities in the Mn 2p spectra on the duplex material. Manganese was found in oxidation states II and V/VI: its film content was not dependent on the bulk composition. (C) 2010 Elsevier Ltd. All rights reserved.

The corrosion resistances and passivation of austenitic 316L and duplex 2205 powder metallurgical (P/M) steels, produced by employing gas atomizing and hot isostatic pressing (HIP), have been compared with those of their conventional cast and forged counterparts. The P/M 316L steel is shown to have a significantly higher pitting corrosion resistance than the conventional 316L steel in 0.5 M HCl. Since the chemical composition and the total amount of inclusions were analogous for the two steels, the effect is ascribed to the finer grained microstructure for the P/M 316L steel yielding a better passive layer. This is supported by photoelectron spectroscopy data demonstrating differences between the thickness and composition of the passive layers for the two 316 L steels. Differences in the passivation process were also found for the different steels as three mixed potentials were observed in the polarization curves for the P/M and conventional 316L steels whereas only one mixed potential at about +0.7 V vs. Ag/AgCl was observed for the two duplex steels in 0.5 M HCl. The results indicate that discussions of the shapes of polarization curves and mixed potentials should be based on the anodic and cathodic partial currents, including the reduction of oxygen. HIP:ed P/M steels are clearly well-suited for applications requiring high pitting corrosion resistances.

Fatigue crack growth (FCG) tests were performed to evaluate the fatigue behaviour of forged Ti-6Al-4V in air and high-pressure gaseous hydrogen (15 MPa) at room temperature. The results indicate that the effect of gaseous hydrogen is dependent on the stress intensity factor (ΔK). The FCG rate was unaffected by hydrogen below a critical stress intensity, ΔK* ≈ 20 MPa√m. Above ΔK*, the FCG rate fluctuated and subsequently accelerated at higher ΔK values. The observed behaviour is attributed to the change in the fracture processes. A hypothesis is proposed that describes the FCG behaviour in gaseous hydrogen.

To provide clarity on the poorly-understood mechanism of breakaway oxidation, corrosion of Fe9Cr1Mo steel in pressurised CO2 is quantified and modelled. The temperature range 400-640 degrees C, relevant to nuclear power plants, is emphasised. Attack is in the form of combined oxide scale growth and internal carburisation of the metal. Carbon activity in the metal at its surface exhibits a strong time dependence consistent with the kinetically-limited transport of carbon due to the slow Boudouard reaction. Breakaway is associated with the approach to saturation of the steel with respect to carbon. Diffusion modelling agrees well with steel carbide precipitation observations.

Mechanisms of alloy degradation in a fireside N-S-O-C-H-Cl-Na-K atmosphere at 880 °C were elucidated using SEM-EDS, chemical equilibrium calculations, and XRD. Alloys 310S, 800H/HT, and 600 were studied after 0, 8000, and 16,000 h exposure in a boiler co-firing biomass waste. For 310S and 800H/HT it was shown that nitrogen formed internal Cr nitrides lowering the Cr activity and inhibiting internal alloy Cr permeation, and that NaCl and Na 2 SO 4 reacted with Cr oxide to form chromate and to accelerate the S and the Cl pickup. Alloy 600 showed no nitride or major chromate formation.

Mechanisms of alloy degradation in a fireside N-S-O-C-H-Cl-Na-K atmosphere at 880 degrees C were elucidated using SEM-EDS, chemical equilibrium calculations, and XRD. Alloys 310S, 800H/HT, and 600 were studied after 0, 8000, and 16,000 h exposure in a boiler co-firing biomass waste. For 310S and 800H/HT it was shown that nitrogen formed internal Cr nitrides lowering the Cr activity and inhibiting internal alloy Cr permeation, and that NaCl and Na2SO4 reacted with Cr oxide to form chromate and to accelerate the S and the Cl pickup. Alloy 600 showed no nitride or major chromate formation.

We compare different means of predicting and rationalizing properties of corrosion films aiming at gaining deeper understanding of the behaviour of copper in aqueous and sulphide-containing environments. Purely geometrical tools ranging from mean bulk information to anisotropic and facet-specific approaches are discussed, and their performances compared against DFT-based stability and property evaluations of a range of interfaces arising from combining low-index crystallographic planes of the compounds Cu, Cu2O, and Cu2S. We demonstrate the necessity to consider facet-specific interactions to understand nanolevel differences between Cu2S and Cu2O film behaviour, and that thin films cannot be directly described by bulk properties.

The influence of environmental conditions and corrosion layer characteristics have been investigated on the runoff rate of copper and zinc, used as roofing material. For this purpose, a rain device has been constructed, capable of simulating rain episodes of varying intensity and pH, and used on new and aged copper and zinc panels of varying origin and corrosion product composition. The setup, using artificial rain with a composition resembling the southern and central part of Sweden, has proven to result in realistic runoff rates for all materials investigated. During a rain event, easily soluble corrosion products will be removed in the first rain volume, commonly referred to as the first flush, followed by a more or less constant runoff rate during subsequent rain. The magnitude of the first flush depends on environmental conditions prior Co a rain episode, e.g., length of dry periods and extent of dry deposition, as well as on rain volume and rain intensity. A defect-rich and porous corrosion layer increases the magnitude of the first flush. The total metal runoff quantity increases with decreasing pH for both copper and zinc. In agreement with previous findings outdoors, an effect of patina age can be seen on copper. The laboratory data can be used to explain variations in runoff rate between different sampling periods observed in field data.

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.

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.

Different surface treatments, with and without silver (Ag), of a Ti6Al4V alloy for increased bone bonding ability were investigated and compared with non-treated surfaces. Studies were conducted at 37 degrees C in phosphate buffered saline (PBS, pH 7.4) of varying hydrogen peroxide (H2O2) and bovine serum albumin (BSA) concentrations. Increased levels of metal release and corrosion were observed in the presence of both H2O2 and BSA due to complexation with Ti and Al in the surface oxide, respectively. Ag release was enhanced by the presence of BSA. Galvanic effects by Ag were minor, but possibly observed in the most corrosive environment.

Copper exposed to pure, O-2-free water for several months in glass- and metal-contained, well-controlled systems shows no evidence of corrosion, either through hydrogen evolution or through the occurrence of oxidized copper. The results contradict the interpretation of recent experiments where it has been claimed that copper corrodes in pure, O-2-free water far above the very limited extent predicted by established thermodynamic data. Reasons for the different experimental outcomes are discussed. Experimental and theoretical efforts to identify hitherto unknown, potentially corrosion driving species of the Cu-O-H system and studies of copper/water surface reactions are reviewed as background for the present study.