Passivity breakdown of 316L stainless steel during potentiodynamic polarization in NaCl solution.

Time-of-flight secondary ion mass spectroscopy (ToF SIMS) analysis was performed on 316L stainless steel polarized potentiodynamically up to different potentials in NaCl solution. The surface film thickness increased with the ending potential of the potentiodynamic polarization, when estimated by the oxygen ion depth profiles. The chloride ion intensities at the film/metal interface were correlated with the ending potentials during the potentiodynamic polarization and cumulative anodic charge densities that govern the pit initiation. The results and analysis support the passivity breakdown mechanisms considering the role of chloride ions at the metal/film interface, rather than at the film/solution interface. [ABSTRACT FROM AUTHOR]