Anodic/Cathodic Electrical Pulse Treatment of Stainless Steel in Various Mediums and Its Influence on Corrosion Resistance

Electrochemically induced annealing (EIA) is a method to improve the corrosion resistance of stainless steel with a series of anodic/cathodic electrical pulses. However, the treatment solution of sodium nitrite is a kind of carcinogen, and the only medium confines the industrial application of the treatment. Stainless steel samples were treated in several solutions with a series of anodic/cathodic electrical pulses in the present work. The changes of the corrosion resistance and surface microscopic structure of the steel after the treatment and the mechanisms were studied with XRD, metallographic observation, cyclic voltammetry test and potentio dynamic scanning. Results showed that EIA phase transformation could occur in mediums other than sodium nitrite, such as sodium carbonate. Nitrogen is not an essential condition for the EIA phase transformation. Efficiency of the treatment in 1 mol/L sodium carbonate solution could be improved by reasonable prolonging the cathodic intervals of the electrical pulses. Pitting sensitivity of the steel in sodium chloride solution could also be reduced with the EIA treatment in the sodium carbonate solution. However, the electric pulse treatment in solutions of sodium sulfite, sodium silicate and sodium acetate caused preferential corrosion of the martensite in the steel.