npj Materials Degradation最新文献

This study examines hydrogen permeation and trapping in three types of natural gas pipeline steels from different decades in Canada-modern, vintage, and legacy steels. Electrochemical permeation experiments were conducted to measure the diffusion coefficient, subsurface concentration, and trap density of hydrogen. The results were analyzed to evaluate the susceptibility of these steels to hydrogen embrittlement and to understand the effects of hydrogen on their mechanical properties. Vintage steel exhibited 50% higher steady-state permeation current and 97% greater effective diffusivity compared to modern steel, while legacy steel showed intermediate values. Hydrogen diffusion increased with grain size and pearlite content but decreased with dislocation density. Modern steel demonstrated the highest resistance to hydrogen permeation due to its finer grain structure and higher dislocation density. This study provides essential insights into the diffusion behavior and trapping mechanisms of hydrogen in natural gas pipeline steels, enhancing the understanding of material performance under hydrogen exposure.

A phase-field model is developed to simulate intergranular corrosion of ferritic/martensitic steels exposed to liquid lithium. The chromium concentration of the material is used to track the mass transport within the metal and liquid (corrosive) phase. The framework naturally captures intergranular corrosion by enhancing the diffusion of chromium along grain boundaries relative to the grain bulk with no special treatment for the corrosion front evolution. The formulation applies to arbitrary 2D and 3D polycrystalline geometries. The framework reproduces experimental measurements of weight loss and corrosion depth for a 9 wt% Cr ferritic/martensitic steel exposed to static lithium at 600 °C. A sensitivity analysis, varying near-surface grain density, grain size, and chromium depletion thickness, highlights the microstructural influence in the corrosion process. Moreover, the significance of saturation is considered and evaluated. Simulation results show that near-surface grain density is a deciding factor, whereas grain size dictates the susceptibility to intergranular corrosion.

At the Ballidon experiment, one of the longest running glass durability studies, modern and simulant archaeological glasses were buried in mildly alkaline, under-saturated, conditions for 52 years. Glass surfaces were analysed to determine the extent and mechanisms of alteration. Alteration layer chemistry was complex and included Ca from the surrounding limestone sediment and P from porewater resulting in Ca, Pb and Fe-phosphate rich phases interspersed with Si and Al rich regions. There was evidence for ongoing evolution of the alteration layer structure due to continued fluid ingress. Lamellae in the silica-rich regions approximately numbering the years of burial and indicating a possible link between their formation and seasonal climate cycling. Comparison of field samples with laboratory dissolution tests highlighted the impact of surface finish on initial alteration rate and the limitations of using alteration layer thickness to estimate the amount of glass that has dissolved.

Understanding biocide performance in mixed-species biofilms is critical to mitigating microbiologically influenced corrosion (MIC). In this study, a novel dual anaerobic biofilm reactor was used to evaluate glutaraldehyde efficacy under environmentally relevant conditions, using a complex microbial consortium from marine sediment. Despite biocide dosing, biofilms persisted and induced localized corrosion, indicating incomplete mitigation. Each biocide application led to an electronegative shift in E _corr and a reduction in $H_{2}S$ concentration, suggesting partial suppression of microbial activity. Raman spectroscopy and profilometry revealed differences in corrosion product composition and pit morphology between biotic and abiotic systems. 16S rRNA sequencing showed enrichment of stress-tolerant genera, including Exiguobacterium and Serpentinicella, consistent with increased chemical tolerance. These findings highlight the limitations of conventional biocide strategies and demonstrate the need for adaptive, community-informed treatment approaches. The dual-reactor model provides a robust platform for future MIC standardization efforts and mechanistic investigation of biofilm resilience under anoxic conditions.

The corrosion of iron or steel in contact with bentonite is a key factor affecting the long-term safety of radioactive waste disposal system. Previous studies focused on corrosion after long-term burial in compact bentonites, however, little work was dedicated to the corrosion of iron exposed to bentonite slurries, that can appear in case of fracture of the bentonite jacket separating steel from underground water. In this study, accelerated corrosion experiments were performed on pure iron in basic bentonite slurries (pH 9-10) using various electrochemical corrosion techniques. The anodic dissolution of iron was larger in more concentrated bentonite slurries and resulted in the formation of an acidic gel. This gel results from a cationic exchange between Fe²⁺ ions released by corrosion and protons from surface or edge locations in bentonite. Its growth appears to be governed by reactions at the gel-bentonite interface rather than diffusion processes.