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This paper contrasts metastable and stable pitting of 316 austenitic stainless steel in chloride and bromide bearing solutions. Metastable and stable pitting characteristics were evaluated by potentiostatic and potentiodynamic polarization experiments, respectively. Results revealed that for a given concentration of halide anions, pitting and repassivation potentials rise by increasing the Br − :Cl − concentration ratio in the environment. Increasing the relative concentration of Br − also leads to a decrease in the values of metastable pit stability product. Furthermore, higher concentration of bromide in the solution reduces the growth kinetics of metastable pits. Using pencil electrodes, it was also found that hindrance of the dissolution reactions in presence of bromide anion could be responsible for the lower aggressivity of bromide and the observed decrement in metastable growth kinetics.

This paper intends to evaluate the pit chemistry characteristics of 316 austenitic stainless steel in NaCl and NaBr solutions while discussing the pitting transition from metastability to stability. Results reveal that increasing the relative concentration of bromide increases the critical and saturation concentrations of cations, which are, respectively, requisites for pit survival and salt precipitation. Besides, bromide causes the ohmic solution resistance of the pit solution to increase. Consequently, it intensifies the pit transition from metastability to stability and retards the occurrence of the stable pitting. The morphology of the pits and the influence of the pit lacy cover on the pit stabilization in NaCl and NaBr solution are also discussed. It was also observed that contrary to metastable pits, salt-covered stable ones have higher growth kinetics in the presence of bromide.

Dependence of 2205 duplex stainless steel pitting resistance on its microstructure was investigated using microstructural examinations and potentiodynamic and potentiostatic polarization techniques. An as-received hot-rolled alloy was subjected to different heat treatments to understand how microstructural characteristics individually affect the corrosion resistance in terms of critical pitting temperature (CPT), pitting potential (E pit), and metastable pitting characteristics. Results revealed that there is a transition temperature interval for the 2205 DSS. By promoting pit initiation and pit propagation, the Widmanstätten structure significantly deteriorated both CPT, by 10 °C, and E pit, compared to the as-received hot-rolled specimen. The σ phase appearance was also associated with a minor drop in CPT, but a considerable reduction in E pit as it increased the occurrence frequency of metastable pits. The specimen having equiaxed grains had the highest CPT, underwent stable pitting at 47 °C, but still it had a low E pit compared to the hot-rolled specimen due to its higher occurrence frequency of metastable pits. The formation of the Widmanstätten austenite needles weakened the ferrite phase in terms of the pitting resistance by reducing the contents of Cr and Mo in it and made it more susceptible to pit propagation.

Electrochemical energy conversion devices are considered key in reducing CO2 emissions and significant efforts are being applied to accelerate device development. Unlike other technologies, low temperature electrolyzers have the ability to directly convert CO2 into a range of value‐added chemicals. To make them commercially viable, however, device efficiency and durability must be increased. Although their design is similar to more mature water electrolyzers and fuel cells, new cell concepts and components are needed. Due to the complexity of the system, singular component optimization is common. As a result, the component interplay is often overlooked. The influence of Fe‐species clearly shows that the cell must be considered holistically during optimization, to avoid future issues due to component interference or cross‐contamination. Fe‐impurities are ubiquitous, and their influence on single components is well‐researched. The activity of non‐noble anodes has been increased through the deliberate addition of iron. At the same time, however, Fe‐species accelerate cathode and membrane degradation. Here, we interpret literature on single components to gain an understanding of how Fe‐species influence low temperature CO2 electrolyzers holistically. The role of Fe‐species serves to highlight the need for considerations regarding component interplay in general.