The nucleation and growth of metastable pitting on pure iron

The nucleation and growth of metastable pitting on pure iron surface in NaNO2 + NaCl solution were investigated by potentiodynamic tests. The current fluctuations appear as cluster and overlapped. The active sites for nucleation depend mainly on the surface geometry. The growth behaviour of pure iron is different from stainless steels and carbon steels. On pure iron surface, many pits pile up together to form huge damage area. Pits are shallow, do not grow deeply and pits array one by one along the direction of abrasion grooves. The growth of stable pitting is different from metastable pitting.