Electrochemical behaviour of Mo-containing austenitic stainless steels in buffer solution

The effect of pH on the electrochemical behavior of austenitic stainless steels in naturally aerated and nitrogen-deaerated buffer solutions has been studied. Potentiodynamic and ac impedance techniques were used. The results indicate that corrosion current (I-corr) decreases with pH. By examining the impedance data for the seven tested steels under various conditions, it seems that the total resistance (R-T) value is a suitable indication parameter for explaining the role of molybdenum and the other supplementary alloying additions (Ni, N, Cu and Mn) on the passive film behaviors as a function of pH of the forming solutions. As a general trend, the R-T values for all steels tended to be lower in the basic buffer than in the acidic solutions.