Pit formation on the Fe-13Cr alloys in chloride solutions

The kinetics of initial local depassivation of iron-chromium alloys is researched in chloride-containing borate buffer. Alloys the Cr concentration of which correlates with a critical area, indicate a variation in the type of concentration dependence of the pitting potential E. The E as a function of NaCl concentration for Fe-10-13%CR is governed by the Cr content in a superficial layer when the film is dissolved by chloride. The potential dependence of the induction period τ0 at various chloride concentrations is discussed. The value of τ0 is proportional to the rate constant for chemical interrelation between an anion-activator and the electrode surface under steady electrostatic factors.