Growth of single corrosion pit in sputtered nanocrystalline stainless steel film

• Temperature controlled potentiostatic polarization was used to initiate single pit.
• The pit formed on sputtered NCss film shows two-step growth behavior.
• An appropriate model was set up to simulate the pit growth.
• Both of the pit growth rate and current density at each stage are constant.
• A special structure configuration of the pit cover was observed.

A single stable pit was initiated on the sputtered nanocrystalline stainless steel film. The pit shows two-step growth behavior. The pit growth rate and current density at each stage are constant. The interior morphology of the pit was observed. A series of outward-tilted concentric pit walls on the backside of the pit cover was discovered for the first time. These walls showed a constant spacing and presented an extremely regular configuration. Besides from the vestige of unreacted metal, the pit cover also contained the passive film which had originally covered the metal surface.