External control of anodic dissolution mechanism of 100Cr6 in nitrate/chloride mixed electrolytes
The anodic dissolution of 100Cr6 steel in neutral electrolytes containing sodium chloride and sodium nitrate was investigated potentiodynamically and galvanodynamically with a rotating disc electrode at room temperature. The total concentration of the mixed electrolyte was 3 mol L-1 with variation of chloride/nitrate mole ratios. The potentiodynamic linear sweep voltammograms (LSVs) in mixed electrolytes are similar to the LSVs in pure chloride electrolyte at lower current densities and switch to behaviour observed in pure nitrate electrolytes at higher current densities. Provided that both anions are present, it seems that the dissolution reactions at the steel anode are determined by the interface layer only. The effect of these layers on surface quality and current efficiency was also investigated in a flow channel applying galvanostatic pulses. An evidence for different dissolution mechanisms can be seen with an important influence of duty cycle and flow conditions. This allows external control of the desired dissolution mechanism in mixed electrolytes.