Pitting Corrosion Behaviors of 304 Stainless Steel by Studied Spatial Electrochemical Scanning Microscopy

Pitting corrosion process of 304 stainless steel in NaCl solution was investigated using scanning electrochemical microscopy (SECM), combined with the measurements of electrical conductivity and cyclic voltammetry. The results showed that there were meta-stable electrically active sites on the surface of stainless steel in the initial pitting process. In the formation process of pits, some initiated meta-stable electrically active sites might disappear, some might propagate and finally become stable pits, while new ones might be induced. The generation, disappearance of meta-stable electrically active sites and formation of pits occurred simultaneously. The electrical conductivity of NaCl solution was related with the concentration of Fe2+ in the solution. The higher the concentration of Fe2+ in NaCl solution, the greater the steady-state current detected by superfine electrode probe.