The pitting corrosion behavior of HRB400 steel in various simulated concrete environments was investigated by the combination of polarization curves and statistical method. The results indicated that the chloride concentration threshold ([Cl⁻]_th) for pitting of the steel was greatly affected by pH when the applied potential exists, which is always caused by random stray current. The interaction of applied potential and chloride concentration on the pitting behavior was discussed. Finally, pitting-risk-evaluation diagrams were built up, which could be easily used to assess the pitting risk of reinforcing bars under the chloride-containing environment with stray current.

A novel conversion film containing cerium and molybdenum was synthesized on the rebar surface, and then the pitting sensitivity of the rebar was improved in a concrete environment containing chloride. This conversion film presented a two-layer structure, which involved CeMoO_x as the outer layer and FeO_x as the inner layer. The film with two-layer structure exhibited a strong corrosion resistance after being immersed in an alkaline environment (pH = 12.5) added with 0.1 M NaCl, and the charge transfer resistance (R _t) could reach 5.88 × 10⁶ Ω·cm² after immersion for 1600 h, which was approximately 2.5 times the initial R _t value. Moreover, it was found that the film has a self-heal property when being damaged beyond the pitting potential. The anticorrosion mechanism of the film and its self-healing mechanism were discussed in depth in this study.

An orthogonal experimental design was combined with electrochemical measurements (OCP and potentiodynamic polarization), microstructural characterization (SEM/EDS and XRD), and COMSOL finite element simulations. The combined effects of applied tensile stress, scratches in the anodic oxide film, and NaCl concentration on corrosion at defects in anodized 7A04-T6 aluminium alloy were systematically investigated. Electrochemical corrosion at oxide film defects was governed by the coupled effects of stress, defects and NaCl concentration. Their effects on the corrosion rate ranked as follows: applied stress > scratch size > NaCl concentration. The defects produced a distinct low-stress region outside the scratch and stress concentrations along its inner edges. Galvanic coupling between these regions accelerated anodic dissolution of the substrate in the stress-concentrated region. Large scratches (6 mm) further amplified local galvanic effects, whereas increasing NaCl concentration initially promoted and subsequently inhibited corrosion. Under the combined conditions of a 6 mm scratch, a tensile stress of 50% of the yield strength, and 3.5% NaCl, simulations yielded a characteristic inner-edge equivalent stress of 559 MPa, distinct from the highly localized maximum of 1340 MPa near a sharp geometric discontinuity. The anodic equilibrium potential at the inner edge was -0.758 V, compared with -0.747 V at the low-stress outer edge. These results suggest that local electrochemical differences promote preferential dissolution in stress-concentrated regions and may contribute to further corrosion damage.