LOCAL DEPASSIVATION OF BINARY IRON-ALLOYS CONTAINING UP TO 25-PERCENT CHROMIUM

Electrochemical methods and Auger electron analysis are used to study the initial stages of pitting on iron alloys containing up to 25% chromium in aqueous halide solutions. The study is conducted within a broad range of temperatures. The dependences of E(pt), and tau0 on the concentration of solution anions and the chromium content of the alloy are determined The results are explained on the basis of the proposition that the potential drop is localized in the chromium-containing layer of the oxide film formed in the halide solution. The enhanced properties of this surface layer govern the kinetics of the initiation of pitting on Fe-Cr alloys.