STUDY OF DISSOLUTION MECHANISMS OF NICKEL IN SULFURIC-ACID-SOLUTION BY ELECTROCHEMICAL QUARTZ-CRYSTAL MICROBALANCE

Investigations of nickel dissolution in sulfuric acid solution have be en 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 region s at low anodic overvoltages and the transpassive dissolution region a t high anodic overvoltages. The comparison of EQCM response with trans ient current indicates that the final products in the two active disso lution 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) 19 97 Elsevier Science Ltd.