Effect of structural heterogeneity on stable pit growth of Co-based metallic glasses

Abstract

The artificial pit technique was employed to investigate the stable pit growth of Co68.15Fe4.35Si12.5B12Cr3 metallic glasses (MGs) exposed to 0.6 M NaCl solution. Critical parameters of pit growth stability were assessed to clarify the correlation between structural heterogeneity and stable pitting kinetics. Thermally induced degeneration of structural heterogeneity increases the repassivation potential and critical pit solution concentration required for pit survival, thus strongly inhibits the activation-controlled growth of salt-film-free pits. Nevertheless, the inhibitory effect on the diffusion-controlled growth of salt-film-covered pits is relatively weak, as revealed by the fact that the saturation concentration required for salt precipitation remains unaffected.