Corros. Mater. Degrad., Volume 7, Issue 2 (June 2026) – 7 articles

Concentrated Solar Power (CSP) tower systems require receiver materials capable of operating above 1000 °C to meet the efficiency targets of third-generation technologies (25–30%). Hybrid solutions, combining ceramic coatings with metallic substrates, offer promising thermomechanical stability under severe thermal cycling. This study investigates the high-temperature behavior of silicon carbide (SiC) coatings deposited on Fe-C-Al-Mo alloys under concentrated solar flux. Substrates were pre-oxidized to form a continuous 1–2 µm α-Al₂O₃ interlayer, serving as a chemical and mechanical buffer. SiC coatings (10–24 µm thick) were deposited via High-Temperature Chemical Vapor Deposition (HT-CVD). Characterization using XRD, SEM, EDS, and optical spectrophotometry identified cubic 3C-SiC with a globular microstructure and high compressive residual stresses (−2000 to −2400 MPa), inducing microcracking. Stress relaxation was achieved by increasing coating thickness or post-deposition annealing. Controlled oxidation formed a thin silica layer, enhancing solar absorptivity to over 90%. Accelerated thermal cycling (up to ~900 kW/m², 1050–1200 °C) revealed that coating stability depends on SiC thickness, residual stress evolution, α-Al₂O₃ interlayer thickness, and cycling severity. Optimizing these parameters is essential for ensuring the long-term durability of hybrid CSP receivers. Full article

Models are described for calculating the crack initiation times for Alloy 600 and Type 304 SS in PWR and BWR primary coolant circuits, respectively. In PWRs, initiation is defined in terms of the grain boundary oxidation concept of Scott and Le Calvar, whereas in BWRs, cracks are envisioned to nucleate from corrosion pits. In contrast, in BWRs, we envision cracks to nucleate from corrosion pits, with the difference in the two systems being primarily due to electrochemical factors. Thus, in BWR primary coolant and the absence of hydrogen water chemistry (HWC), the oxidizing conditions due to the radiolytic production of H₂O₂ cause the ECP to be significantly more positive than the critical pitting potential. Accordingly, the nucleation and growth of pits due to passivity breakdown and the establishment of differential aeration between the pit nucleus’s internal and external environments, which results in growth of pits to the critical size necessary to satisfy the Kondo criteria for transition of a pit into a crack, is judged to be a realistic scenario. Contrariwise, in PWR primary coolant, the ECP is so negative [≈−1.0 V_she] due to the large amount of pressurizing H₂ present in the circuit [20–60 cm³(STP)/kg H₂O] that the nucleation and growth of pits is not possible. However, Totsuka and Smialowska found that MA Alloy 600 suffers hydrogen-induced cracking (HIC) at an ECP < −0.85 V_she, demonstrating that, in service with a high hydrogen concentration, brittle fractures will occur. The initiation sites were not identified. The crack initiation models for Alloy 600 in PWRs and Type 304 SS in BWRs reproduce the effects of the following independent variables: applied stress, temperature, cold work, grain boundary segregations, water chemistry, pH, and electrochemical potential. The origins of the observed scatter in experimentally measured crack initiation times are discussed, and the challenges of developing a more general crack initiation model (GCIM) are identified. From a mathematical viewpoint, the most significant challenge arises from the nested distributions involving the many parameters and expressions within the GCIM that are either distributed because of an imprecise definition or because some experimentally determined input parameters are experimentally scattered. Additionally, the evolution of semi-elliptical surface cracks resulting from the electrochemical crack length (ECL) being shorter than the classical mechanical crack length (MCL) must be incorporated if the GCIM is to find utility in the water-cooled nuclear power industry where semi-elliptical surface cracks are normally observed. Full article

This study analyses the behaviour of brass CB773S with extra-low-lead content in relation to corrosion and the corrosion–cavitation phenomenon. Electrochemical corrosion tests, both potentiodynamic and potentiostatic, as well as corrosion–cavitation tests, were conducted. Various potentials were applied to brass, alongside cavitation generated by an ultrasonic bath. Artificial seawater and artificial brackish water were used as electrolytes. Surface damage was evaluated using a stereo microscope and scanning electron microscopy. The results indicate that the interfaces between alpha and beta phases of brass serve as preferential sites for the nucleation and collapse of vapour bubbles under cavitation conditions, leading to a deep pitting, especially in artificial brackish water under this synergy. Susceptibility to a selective corrosion of the Zn-rich phase was observed, highly dependent on the test solution, as well as on the applied potential during the tests. The corrosion–cavitation synergistic damage was strongly dependent on the electrochemical parameters, particularly the applied potential, which plays a key role under cathodic protection conditions. In general, it can be concluded that low-lead brass behaviour is governed by a complex interaction between applied potential, electrolyte chemistry, microstructure, and mechanical effect. These findings provide valuable insights into brass’s performance under service conditions where corrosion and cavitation may appear simultaneously in marine environments. Full article

For the corrosion behavior of three extruded Mg alloys (WE43, Mg10Gd, ZX10), the corrosion morphology and the resulting local stress distribution are correlated with the residual strength using µCT, Digital Image Correlation and tensile tests. Samples are corroded in HBSS at 37 °C for various exposure times to increase the extent of corrosion. They are then examined by using the gravimetric method to determine the corrosion rate. Corroded tensile samples are subjected to µCT analysis before and after tensile testing. The crack formation originating from pitting corrosion is discussed on the basis of the stress distribution around local corrosion—its extent is clearly influenced on the morphology. µCT analyses reveals that fractures occur in different ways, either at the smallest cross section, at isolated deep pitting sites, or in other critical areas with critical pitting quantity or size. Mg10Gd has a slightly higher strength compared to WE43 and ZX10. ZX10 maintains superior residual strength over time. Pitting corrosion is mainly observed in Mg10Gd and WE43, with different degrees of residual strength. This study allows for a better understanding and prediction of critical areas of non-uniform corroded Mg alloys and provides information on the bearable stress concentration. Full article

This study proposes a new deep learning-based approach for detecting pitting corrosion on stainless-steel sheet pile surfaces in drainage channels. Conventional ultrasonic thickness measurement methods cannot detect microscopic pitting corrosion that occurs before measurable thickness reduction. The research develops an automated detection system using visible images captured with smartphone cameras and U-net semantic segmentation. Two stainless steel grades (SUS410 and SUS430) were exposed for 5 years to a brackish water environment and analyzed. The deep learning approach achieved F1-scores of 0.831 (SUS410) and 0.808 (SUS430), outperforming binary thresholding methods (F1-scores: 0.407 and 0.329, respectively). Data augmentation improved performance by 1–3 percentage points. The method enabled non-destructive, quantitative assessment of early-stage corrosion using readily available equipment, providing a practical tool for infrastructure maintenance and long-term durability evaluation. Full article

Flashover events can induce rapid surface condition changes on outdoor ceramic insulators, while early-stage degradation is typically assessed indirectly through long-term ageing or electrical diagnostics. This study proposes an event-based, surface-focused evaluation framework to assess short-term flashover-induced surface degradation using normalized wettability indicators. A controlled experimental comparison was conducted on uncoated, TiO₂-RTV-coated, and SiO₂-RTV-coated 150 kV ceramic insulators subjected to a single flashover pre-stress under humid tropical conditions. Static contact angles decreased from 42.6° to 18.3° for uncoated ceramic, from 112.4° to 86.7° for TiO₂-RTV, and from 115.8° to 92.6° for SiO₂-RTV after flashover exposure. The corresponding relative wettability retention values were 43.0%, 77.1%, and 80.0%, while the wettability degradation index values were 0.57, 0.23, and 0.20, respectively. Surface morphology and elemental presence were qualitatively examined via SEM–EDS. The results show that both nanocomposite coatings effectively preserve post-flashover surface hydrophobicity compared with uncoated ceramics, with the SiO₂-RTV system exhibiting the highest short-term wettability retention. By integrating static contact-angle measurements, qualitative surface morphology, and normalized wettability indicators, this study proposes an event-based evaluation framework for RTV-coated ceramic insulators. Flashover-voltage and leakage-current measurements were included only as supplementary validation to support the surface-based interpretation, without implying direct electrical performance modeling. This surface-focused, event-based approach provides an experimental basis for post-flashover condition assessment of ceramic insulators operating in humid outdoor environments. Full article