Stoichiometry of anodic nickel dissolution in NaCl and NaClO 3 under active and transpassive conditions

Abstract

The anodic dissolution of nickel 200 at very high current densities has been investigated in 1N NaClO 2, 1N NaCl and in mixtures of the two electrolytes by measuring potentiostatic current potential curves and by determining the current efficiency for metal dissolution from weight loss measurements. In 1N NaCl Tafel behavior was found up to 0·5 A/cm 2. In 1N NaClO 3 no active dissolution region was observed, but substantial transpassive dissolution occurred at current densities above 2 A/cm 2. The presence of chloride ions led to pitting and to an increase in anodic dissolution rate. Apparent current efficiencies based on divalent nickel formation even exceeded 100 per cent, indicating that the chlorate ion was decomposed at the anode.