Abstract CO 2 curing can greatly enhance the properties of concrete while actively sequestering CO 2 . However, the influencing mechanisms of CO 2 curing on the passivation film of steel bars in concrete remains unclear. In this study, the passivation and depassivation behaviors of steel bars in CO 2 -cured mortar were investigated via electrochemical measurements, and the microscopic morphology and chemical composition of the passivation film were examined using scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The results demonstrate that CO 2 curing can accelerate the passivation of steel bars, which can be attributed to the higher oxygen partial pressure around the steel bars when compared to standard curing. Although the thickness of passivation film on steel bars in CO 2 -cured specimens (4.06 nm) is less than that in standard-cured specimens (4.73 nm), the charge transfer resistance in CO 2 -cured specimens (458.54 kΩ·cm 2 ) is higher than that in standard-cured specimens (384.49 kΩ·cm 2 ). Specifically, the dense and ordered microstructure observed by SEM, together with the relatively high Fe 2+ /Fe 3+ atomic ratio (0.90 vs. 0.63) of the passivation film detected by XPS, contributes to the enhanced electrochemical stability. In addition, it is found that CO 2 curing significantly delays the depassivation onset of steel bars in mortar when subjected to chloride drying-wetting cycles, with the depassivation of standard-cured specimens initiating after 18 cycles and that of CO 2 -cured specimens being postponed to 30 cycles. Consequently, the protective performance of the passivation film in CO 2 -cured specimens surpasses that in standard-cured specimens despite the slightly thinner thickness.

Abstract A modelling approach that combines a previously developed 2D continuum finite element model with machine learning to support the design and evaluation of corrosion-inhibiting coatings. The FEM simulates the leaching of corrosion inhibition pigments from an organic coating and the resulting protection of the metal surface. This is conducted for a system of aluminium alloy 2024-T3 with an active protective coating loaded with lithium carbonate particles. A generated dataset from FEM results was used to train ML models to predict inhibitor concentration and corrosion current density based on geometric and material input parameters. A feature importance analysis was conducted to identify the most influential input variables, providing insight into the factors controlling the achievement of corrosion inhibition. Furthermore, a blind test was performed using five unseen cases that were not involved in the training phase. Finally, the trained models were applied to explore their use in coating design.

Abstract Salt-spray testing is widely used in the automotive and materials industries to assess the corrosion resistance of protective coatings, where uniform corrosion is a key indicator of material performance. This work presents a numerical uniform corrosion model that predicts the corrosion rate of hot-dip zinc in salt-spray environments by incorporating electrochemical reactions, mass transport via the Nernst–Planck equation, and ionic-strength effects through the Brønsted–Bjerrum relation. The model is calibrated using immersion-test data and extended to account for electrolyte layer growth, droplet deposition, and periodic run-off in salt-spray environments. The calibration establishes a relationship between the porosity of the zinc oxide layer and the rate constant of zinc oxide precipitation. The validated model reproduces the transition from activation- to diffusion-controlled corrosion and captures the experimentally observed corrosion kinetics with an error margin of 20% when electrolyte renewal is included. The results highlight the decisive role of electrolyte dynamics in salt-spray environments and provide a foundation for extending the framework to more complex cyclic corrosion tests.

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.

Abstract The mechanism of the inhibition of pitting corrosion in Type 304 stainless steels by NaNO 3 is investigated in 0.1 M NaCl. The addition of 10 mM NaNO 3 inhibits stable pit initiation at CaS and MnS inclusions under potentiodynamic anodic polarization. However, NH 4 Cl and NaNO 2 do not improve the pitting corrosion resistance. In the initial steps of pitting corrosion at MnS in 0.1 M NaCl, no effect is observed on the MnS dissolution and trenching at the MnS/steel boundary; however, NaNO 3 is found to inhibit the active dissolution of the steel matrix in 0.5 M HCl, which is intended to simulate the interior of pits. This inhibitory effect on active dissolution is also observed in 0.5 M HCl–10 µM Na 2 S 2 O 3 , where elemental sulfur, a dissolution product of MnS, is generated. In 0.5 M HCl, two active dissolution peaks appear. The current density at the first peak at a lower potential is found to decrease with the addition of NaNO 3 . This behavior is compared with active dissolution in solutions in which the pH and the Cl⁻ concentration were systematically varied, and the mechanism of pitting corrosion inhibition by NaNO 3 is discussed.