Study of dissolution mechanisms of nickel in sulfuric acid solution by electrochemical quartz crystal microbalance

Investigations of nickel dissolution in sulfuric acid solution have been performed by using an electrochemical quartz crystal microbalance (EQCM). The anodic polarization curve of electrodeposited nickel shows distinct three dissolution regions, i.e. two active dissolution regions at low anodic overvoltages and the transpassive dissolution region at high anodic overvoltages. The comparison of EQCM response with transient current indicates that the final products in the two active dissolution regions are almost Ni(II) and that the Ni(II) dissolution ratio to the total anodic charge in the transpassive dissolution region is smaller than that in the two active dissolution regions. On the basis of reaction parameters obtained experimentally, the active dissolution mechanism of nickel can be explained by the Bockris mechanism. (C) 1997 Elsevier Science Ltd.