ELECTROCHEMICAL-BEHAVIOR OF CERTAIN ELECTROPLATES IN SOLUTIONS FOR COULOMETRIC DETERMINATION OF THEIR THICKNESSES - I - BEHAVIOR OF NICKEL ELECTROPLATES

The anodic behavior of nickel electroplates was studied by potentiodyn amic and chromopotentiometric methods on rotating disk electrodes in s olutions used for the coulometric determination of their thicknesses. The current-maximum height on voltammograms varies in direct proportio n to the electrode rotation rate and in inverse proportion to the conc entration of the main component of a studied solutions, i.e., NH4NO3 o r HCl. Chronopotentiograms obtained at different fixed rates of anodic dissolution reveal a parallel nonfaradaic process, the contribution o f which can exceed the contribution of main electrochemical processes. The anions NO3- and Cl- in the electrolyte, under certain conditions, can behave as depositing anions. On this basis, the existence of nick el nitrate or chloride salt films as the cause of passivation and the accompanying nonfaradaic process, respectively, is supposed. It is sho wn that the solution nitrate composition recommended by ISO for measur ing the thickness of nickel electroplates needs to be specified more p recisely.