Factors affecting on the electrodissolution of Ni in acidic chloride solutions

The anodic dissolution of nickel was studied galvanostatically in hydrochloric acid solutions of various concentrations. The reaction orders with respect to chloride ion and hydrogen ion concentrations were found to be 0.5 and 1.0, respectively. An anodic Tafel slope equal to 120 w 10 mV decade(-1) was obtained. The dissolution rate of nickel at constant acid concentration was increased with stirring of solution and increasing the temperature. The activation energy, DeltaH, for the anodic dissolution process was found to be 12 kcal mol(-1). The presence of oxygen in solutions assisted the passivation process. The effect of addition of aniline and some of its derivatives (o-, m- and p-anisidine) as inhibitors on the dissolution kinetics of Ni in 1M HCl was also investigated. The data revealed that addition of these compounds inhibited the anodic dissolution of nickel without affecting the Tafel slope, indicating that the adsorption of such inhibitors could not interfere with the mechanism of metal dissolution.