Dissolution and corrosion products induced mechanical damage in Al-Zn-Mg-Cu alloy exposed to aqueous corrosion environments

Abstract Borosilicate glasses are key materials for immobilizing high-level nuclear waste. The effect of self-irradiation damage on the structural integrity of the glass and its aqueous corrosion resistance is not yet fully understood. This study investigates a ternary Na borosilicate glass irradiated with ~950 MeV gold ions, producing severe damage within a ~ 50 µm layer, and subsequently corroded in a 0.5 M NaHCO₃ solution at 81.2 °C for 12.5 days. Using operando Fluid-cell Raman spectroscopy and D 2 O as a tracer for water transport through the surface alteration layer (SAL), we observed (i) a 2.5-fold increased initial forward dissolution rate of the irradiated glass, (ii) a further increase of the dissolution rate at the irradiated/non-irradiated interface, (iii) elevated residual dissolution rates, and (iv) variations in the silica ring structures correlating with the changes in the rates. These findings confirm that irradiation enhances glass reactivity and support the interface-coupled dissolution–precipitation model for SAL formation.

Grain boundary versus grain interior aqueous corrosion in iron-phosphorous and iron-copper binary ferritic alloys

ABSTRACT Understanding the corrosion behavior of glass–ceramic composite materials such as Fe‐Al‐BG‐Gd 2 Ti 2 O 7 as potential nuclear wasteform candidates has attracted considerable attention due to their high loading of actinide elements and fission products compared to current borosilicate glass nuclear wasteforms. The result of long‐term corrosion studies on the Fe‐Al‐BG‐Gd 2 Ti 2 O 7 composite material indicated that the Fe‐Al‐BG matrix had higher solubility in deionized water compared to the Gd 2 Ti 2 O 7 phase. This is an important property for composite materials as actinide elements can be incorporated into the Gd 2 Ti 2 O 7 phase. Furthermore, the corrosion resistance of the Fe‐Al‐BG matrix of the Fe‐Al‐BG‐Gd 2 Ti 2 O 7 composite material was found to be comparable to that of borosilicate glass nuclear wasteform on its own. Comprehensive surface analysis of Gd 2 Ti 2 O 7 and Fe‐Al‐BG‐Gd 2 Ti 2 O 7 composite materials demonstrated that the surface composition and chemistry of these materials were affected by aqueous corrosion. However, the results of bulk analysis showed that the bulk structure of these materials remained stable over 365 days of exposure to deionized water. The analysis of XPS data from the Fe‐Al‐BG‐Gd 2 Ti 2 O 7 composite material demonstrated that a precipitated metal‐hydroxide layer has been formed on the surface of the composite material after exposure to water and remained likely unchanged between 270 and 365 days of exposure to water. The stability of the surface layer during this time frame could potentially protect the surface of the Fe‐Al‐BG‐Gd 2 Ti 2 O 7 composite material from further corrosion and suggest this composite material could be considered as a potential alternative substitute to borosilicate glass wasteforms.

Abstract The third element effect draws on the synergy of some ternary systems. FeCrAl is one such alloy system that has shown superior high temperature oxidation resistance. However, the third element effect is understudied in aqueous corrosion. This study systematically explored the passivation behavior 4-16 at.% Al additions to single phase solid solution FeCr 10 alloys and compared their performance to Fe-Cr binary alloys. Additions of Al improved repassivation and long-term passivity of Fe (90-x) Cr 10 Al x alloys in deaerated acidified 0.1 M Na 2 SO 4 or 0.1 M H 2 SO 4 . Characterization via ex-situ X-ray photoelectron spectroscopy and in-operando atomic emission spectro-electrochemistry explored compositions of the films as well as the specific elemental dissolution kinetics into the electrolyte. Oxides or hydroxides consisting of Cr 2 O 3 , Cr(OH) 3 , and Al 2 O 3 improved passivation of Fe 90-x Cr 10 Al x alloys, relative to their ferrous and ferric oxides. The FeCr 10 Al 16 alloy composition behaved similarly to FeCr 16 when considering passivation performance. Even low concentrations of Al resulted in significant performance improvements in the passivity of FeCr 10 compared to binary Fe-Cr alloys with 16 at.% Cr. Discussion of the role of Al in the context of producing a third element effect enhancing Cr(III) passivation and as a secondary passivator itself is considered.

Aqueous corrosion of additively manufactured multi principal element alloys: a critical review

Influence of optimized decarburization on hydrogen uptake and aqueous corrosion behaviors of ultrastrong martensitic steel

Transport phenomena during aqueous corrosion of silicate glass—New insights from theoretical analysis of diffusion with a moving boundary

Assessment of aqueous sulfide corrosion on thermally oxidised copper using surface science techniques

Biofeedstocks derived from living organisms or their byproducts have recently emerged as an environmentally benign complement to petroleum, diversifying energy production in the petroleum industry from sole dependence on crude oil while utilizing mostly existing petroleum infrastructure. However, biofeedstocks also bring challenges as they can cause distinct and potentially more severe corrosion in metal-based petroleum infrastructure than crude oils due to their higher molecular oxygen content and the presence of various organic acids. To effectively manage such corrosion, it is crucial to understand the corrosion mechanism, particularly the onset of local corrosion, as well as its relationship with the metallic microstructure. Here, using pentanoic acid─a typical degradation product and representative corrosion contributor from biofeedstocks─as the corrosive medium, we capture the real-time initiation and progression in corrosion of carbon steel lamella, which is a model petroleum infrastructure, at nanometer resolution. We correlate in situ liquid-phase transmission electron microscopy imaging of the corrosion process with ex situ characterization of grain size, orientation, and elemental distribution. Through this correlative, multimodal characterization, we identify the key microstructural features that significantly influence corrosion behavior: galvanic corrosion initiates corrosion, strain accelerates corrosion, and lattice orientation guides corrosion propagation. Contrary to aqueous corrosion, corrosion in pentanoic acid is not heavily influenced by the grain boundaries, with similar rates observed in coarse- and fine-grain lamellae. Our observations highlight the importance of intrinsic structural features of carbon steel and their impact on corrosion in biofeedstock-based organic acids, providing insights for potential corrosion mitigation.

Experimental investigation and assessment of aqueous corrosion on Stellite cladded Ni, Fe and Cu base alloys

Aqueous corrosion of metals is governed by formation and dissolution of a passivating, multi-component surface oxide. Unfortunately, a detailed atomistic description is challenging due to the compositional complexity and the need to consider multiple kinetic factors simultaneously. To this end, we combine experiments with a first-principles-derived, multiscale computational framework that transcends thermodynamic descriptions to explicitly simulate the kinetic evolution of surface oxides of Ni-Cr alloys as a function of composition, temperature, pH, and applied voltage. In the absence of pitting, we identify three distinct voltage regimes, which are kinetically dominated by oxide growth, dissolution, and competitive dissolution and reprecipitation. Evolving compositional gradients and oxide thickness are revealed, including a transition between a metastable Ni-Cr mixed oxide and a thick, porous Ni-dominated oxide. Beyond elucidating the underlying physics, we highlight the need for competing kinetics in models to properly predict the transition from passivation to corrosion. Our results provide a key step towards co-design of alloy composition alongside environmental conditions for sustainable use across a variety of critical energy and infrastructure applications.

Abstract This study investigates the expansion and deformation characteristics of concrete with varying strengths under the conditions of aqueous solution, wet-dry cycles, and complex salt corrosion environments. The experimental results indicate that under the action of wet-dry cycles, the expansion rate of C30 and C50 concrete specimens in the aqueous solution increases with time, but the overall degree of deformation is relatively small. Due to its higher water-cement ratio, the expansion rate of C30 concrete is generally greater than that of C50 concrete. In a 3% sodium sulfate solution, the expansion rate of C50 concrete is lower than that of C30, which is related to its lower water-binder ratio and denser microstructure. In a 5% sodium sulfate solution, the expansion rate of C30 concrete is significantly higher than that of C50, demonstrating a faster rate of expansion. In the environment of mixed sodium sulfate and sodium chloride solution, the presence of chloride ions effectively mitigates sulfate erosion, reducing the expansion rate. Furthermore, with the increase in sulfate concentration, the expansion and deformation of concrete increase. The expansion and deformation of C50 concrete in sodium sulfate solution are less than that of C30, which is related to its higher tensile strength. The research provides a scientific basis for the durability assessment and protection of concrete structures in sulfate erosion environments.

This study explored the effects of atmospherically formed surface films and surface roughness on Cu corrosion behavior. A comprehensive suite of surface analysis techniques, including X-ray photoelectron spectroscopy, scanning electron microscopy, contact angle measurements, and confocal microscopy, were utilized to characterize the physicochemical properties of the surface films formed over 30 days. Then, both macroscale and droplet electrochemical measurements, such as open circuit potential and linear sweep voltammetry, were performed to explore the films’ effects on the aqueous and atmospheric corrosion behavior of Cu respectively. The results showed that the polarization resistance measured within the droplets was lower than that observed in macroscale experiments, attributable to the varying oxygen diffusion profiles. During atmospheric corrosion, the polarization resistance was dependent on the surface finish due to its impact on the film's composition. Surface characterization revealed the formation of hydroxide and defect oxides that varied between the different surface finishes, resulting in differences in polarization resistances over a 30-day period. However, the films did not affect the polarization resistance measured for samples that underwent aqueous electrochemical corrosion testing, possibly due to their solubility during the open circuit potential period prior to reaching a steady state. This study underscores the importance of surface films on atmospheric corrosion properties and brings skepticism to the need for cathodic cleaning of Cu during aqueous corrosion studies under aerated conditions.

Aqueous corrosion of mild steel is one of the major problems in the oil and gas industry. The current understanding of corrosion mechanisms, mainly focused to the cathodic reaction, was used to build electrochemical models to predict the corrosion rate of mild steel. However, the effect of aqueous CO2 on the anodic iron dissolution reaction was less studied. In contrast, the mechanism of iron dissolution in strong acidic environments has been thoroughly investigated over many decades. Among the proposed mechanisms in the literature, a broadly applicable multi-path mechanism was identified that could explain the behavior of anodic dissolution of iron in strong acidic sulfate solution; both in terms of steady state polarization sweeps and impedance data at various pH values and current densities. However, the role of aqueous CO2 in solutions containing chlorides on the mechanism of anodic reaction had remained an open question.The present study used EIS measurements and ToF-SIMS in-depth profiling and 3D imaging, as the main techniques, to study the mechanism of iron dissolution in strong acid chloride solution with and without the presence of . EIS results showed that the presence of chloride ions (0.5 M) decreases the rate of the anodic iron dissolution and results in the formation of an additional adsorbed intermediate species which participates in the anodic reaction multi-path mechanism in parallel with the other oxide/hydroxide intermediates. The presence of increases the anodic current density mainly in transition and pre-passivation regions, however, EIS investigation of this mechanism showed that aqueous and other carbonic species do not react directly on the bare metal surface and do not form an additional adsorbed intermediate species that is involved in the anodic reaction. Based on EIS results, it is suggested that the presence of aqueous might effect a change of the chemical composition of the adsorbed species (including hydroxide and chloride intermediates), value of kinetic constants and extent of surface coverage by different adsorbed intermediates and ions, leading to the change in the kinetics of the underlying reactions.ToF-SIMS 3D mapping was used to provide supporting evidence for the anodic iron dissolution mechanisms of mild steel in chloride containing aqueous CO2 environments. The technique detected adsorbed hydroxide and chloride intermediates formed during corrosion process, which is consistent with the proposed multi-path reaction mechanism for anodic iron dissolution reaction. Despite the presence of aqueous carbonic species and their observed effect on the kinetics of iron dissolution, no additional adsorbed intermediates have been detected in aqueous environments, indicating that carbonic species do not directly participate in the iron dissolution reaction. ToF-SIMS 3D mapping results further suggest that one role of aqueous carbonic species could be to accelerate the adsorption of chloride ions and formation of chloride intermediates.

This study examines the effects of heat treatment on corrosion behavior of equiatomic AlCoCrNiFe high-entropy alloy within a solution treatment temperature range of 800–1100 °C. Experimental observations on phase formation were compared with thermodynamic predictions. The microstructure, mechanical properties, and aqueous corrosion behavior of the as-deposited alloy were analyzed and contrasted with heat-treated samples. The results showed a decline in the corrosion resistance of the AlCoCrNiFe after heat treatment, which was attributed to chemical segregation and Cr depletion in the microstructure matrix. Additionally, post-corrosion analysis revealed a reduced volume fraction of protective oxides in the heat-treated samples.

An understanding of the anomalously enhanced hydrogen evolution reaction (HER) of magnesium (Mg) under anodic polarisation in aqueous corrosion is paramount for a predictive theory of its corrosion and metal electrocatalysis. Previous theoretical and experimental studies have proposed that sub-surface hydride phases play a role in this behaviour but the underlying atomic mechanisms remain unclear. By constructing theoretical surface Pourbaix diagrams, based on density functional theory (DFT) calculations, we have identified the atomic structure of a sub-surface hydride phase on the Mg (0001) surface that remains electrochemically stable under significant anodic overpotentials across a wide pH range. Specifically, this stability persists up to 0.38 VSHE under mildly alkaline conditions (e.g., pH = 8), thus providing thermodynamic support for the proposed hydride-enhanced HER under anodic conditions. Reaction barrier analysis establishes that the proposed sub-surface hydride phase could promote anodic HER via a Heyrovsky pathway, based on hydrogen outward diffusion, with an energy barrier of 1.54 eV as the rate-limiting step, showing an anodic characteristic and significantly favouring external anodic polarisation. Furthermore, we have established that the surface adsorption condition, contingent on both the pH and potential, significantly influences the mechanism and kinetics of the initial corrosion of Mg.

In this investigation, the aqueous corrosion resistance of 9Cr series heat-resistant steel during tempering was investigated. Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectrometer (EDS) were used to analyze the effect of tempering temperature on the microstructure and precipitation behavior of precipitates. The heat-resisting steel was heated to 1150 °C for 1 h, and then tempered at different temperatures between 680 °C and 760 °C for 2 h. The microstructure of the heat-resistant steel after tempering was composed of lath-tempered martensite and fine precipitates. The hardness decreased with increasing tempering temperature, ranging from HBW 261 to HBW 193. The aqueous corrosion resistance improved as the tempering temperatures increased from 680 °C to 720 °C but deteriorated at higher temperatures, such as 760 °C, which was obtained by an electrochemical corrosion performance test. The aqueous corrosion resistance was affected by the decrease in dislocation density and the decrease in Cr solution in the tempered martensite. With the increase in the tempering temperature, the aqueous corrosion potential first increases and then decreases, the self-corrosion current density first decreases and then increases, and the polarization resistance first increases and then decreases. Furthermore, the increase in corrosion resistance is attributed to the reduction in dislocation density and chromium depletion in the martensitic structure as the tempering temperature approaches 720 °C. This paper reveals the effect of tempering temperature on the corrosion resistance of 9Cr series heat-resistant steel, which is a further exploration of a known phenomenon.

Aluminum and magnesium are the lightest structural metals, and therefore, various alloys based on them are widely used in both, automotive and aerospace industries. However, aluminum and magnesium are very easily affected by atmospheric and aqueous corrosion, and, therefore, the alloying elements should enhance their corrosion stability. In this work, the thermodynamic analysis of phase and chemical equilibria involving aluminum and magnesium alloys doped with silicon in oxygen–containing air environments, as well as the analysis of chemical and electrochemical equilibria involving these alloys in aqueous environments is conducted. The phase and chemical equiliibria in the Al–Mg, Al–Si, Mg–Si, and Al–Mg–Si systems at 298 K are considered, and the thermodynamic activities of the components of common Al–Mg–Si system alloys are calculated. The invariant chemical equilibria in the systems Al–Mg–O, Al–Si–O, Mg–Si–O at 298 K are considered, the isothermal section of the state diagrams of these systems are plotted, and the oxidation scheme of the Al–Mg–Si system alloys in excess oxygen is proposed. The chemical and electrochemical equilibria in the Al–Mg–Si–H2O system at 298 K are considered and presented in form of the activity – pH and the potential – pH diagrams, and the oxidation of the Al–Mg–Si system alloys in aqueous environments is discussed.

Fall 2024 People News features news about Ion Storage, the ECS-sponsored Gordon Research Conference on Aqueous Corrosion, the 8th Baltic Electrochemistry Conference, and remembrances of Dennis H. Evans, Luby Romankiw, and Fred C. Anson