Mechanistic insights into electrochemical-mechanical coupling: PDM-based explanation for accelerated pitting corrosion of 09CrCuSb under low elastic stress

The stress corrosion cracking (SCC) behavior of 09CrCuSb in sulfuric acid (70 wt%) under low constant tensile stress (0, 12, 24 MPa) was investigated. Chemical corrosion immersion, potentiodynamic polarization, and EIS experiments, coupled with XRD, SEM, and EDS analyses, revealed stress-induced localized dissolution accelerates pitting and pseudo-passive film degradation. A mechano-electrochemical model based on the Point Defect Model quantitatively linked stress with enhanced cation vacancy flux, reduced pseudo-passivation stability, and lower critical passivity breakdown potential. This framework advances the mechanistic understanding of SCC during crack initiation, providing valuable insights for predicting and preventing corrosion in industrial systems.