Study of the zinc electroplating process using electrochemical noise technique

The zinc electroplating process was investigated by means of electrochemical noise (EN), cyclic voltammetry and steady-state polarization methods in conjunction with the scanning electron microscopy (SEM) technique. It was found that the EN generated during the electroplating of dentritic or large conglomerate zinc deposit has large potential oscillation amplitude and positive potential drift while the compact zinc deposit possesses small noise amplitude and little potential drift. Meanwhile, the electrocrystallization EN time-domain records were analyzed using wavelet transform technique, the results shown that, with the change of the rate determining step of zinc electroplating process from diffusion-control through mixed-control to activation-control, the maximum relative energy of the EDP (relative energy distribution plot) obtained from wavelet analysis shifted from the region with larger scales to those with smaller scales, and the corresponding deposit structure changed from dentritic to compact, i.e., the EDP can be used as “fingerprints” of EN to characterize the electroplating process and the deposit structure. The results also shown that electrochemical noise technique can give more information about the deposit structure than other normal electrochemical measurements, such as linear potential sweep method and cyclic voltammetry technique.