A quantification of the localized corrosion behavior of , Metglass 2826 A as a function of surface finish and heat‐treatment by cyclic potentiodynamic anodic polarization, potentiostatic polarization, and pit propagation rate (PPR) testing was performed in , at 303 K. The concept of a breakdown potential for pit nucleation similar to that observed in crystalline materials appears to apply to metallic glasses. Values for the protection potential in Metglass 2826A as a function of surface finish or thermal treatment were obtainable by PPR testing. Among the techniques studied, PPR testing appears to give the most consistent results. Auger analysis of films formed in the passive and passive‐transpassive transition show marked changes in elemental film composition and distributions. Resistance to pit nucleation was correlated with changes in the partitioning of elemental species and interactions in the film above and below the breakdown potential. Passivity is maintained for a strong positive (+) Cr‐B association and by interactions, (−) P‐B, (+) Ni‐P, (+) Fe‐P, which promote the formation of a Cr‐B complex. Pitting in Metglass 2826A ensues by changes in the oxidation state of Cr combined with metalloid‐metalloid mixing, (+) P‐B, metal‐metalloid mixing, (+) Ni‐B, and metal‐metal mixing of Cr {(+) Ni‐Cr, (+) Fe‐Cr}. S was the aggressive specie responsible for pitting in Metglass 2826A.