Anode Polarization Effects of Nickel in Sulfuric Acid

Abstract

The electrochemical polarization effects at nickel anodes in 2N sulfuric acid were studied to determine the nature of the electrode reactions involved. Current densities below and above that required to passivate a nickel anode were used. There was evidence of an anodic film forming at the active nickel surface prior to the onset of passivity. In the passive state, the anode reaction was the discharge of hydroxyl ions and subsequent evolution of oxygen gas and formation of a nickel oxide. The presence of chloride ions had the effect of raising the minimum current density required to passivate a nickel anode and delaying the onset of passivity above this current density. The nickel oxide formed anodically was soluble in the acid solution and controlled the rate of polarisation decay.