ELECTROCHEMICAL AND SPECTROSCOPIC STUDIES ON DEZINCIFICATION OF ALPHA-BRASS .2. EFFECT OF POLARIZATION ON THE DEZINCIFICATION PROCESS

The phenomenon of dezincification of alpha-brass in 4% NaCl solution (synthetic sea water) following polarization at various potentials was studied using XPS and AES surface analytical techniques. The electrolyte was simultaneously analyzed by atomic absorption. At potentials more negative than the steady state open-circuit potential (E(st)) of brass, dissolution of both copper and zinc was restricted by the values of the solubilities of Cu2O and ZnO. At potentials more positive than E(st) dissolution of alpha-brass occurred with 100% current efficiency with a rate two orders of magnitude higher than that measured at negative potentials. XPS analysis of the alloy surface following polarization proved the formation of CuCl and two forms of ZnO. Dissolution of copper is assumed to occur through CuCl2 - where that of zinc is suspected to occur through HZnO2. The two metals go into solution in a ratio comparable to that of the alloy. Following prolonged polarization, xps spectra indicated the redeposition of metallic copper from solution on top of the CuCl precipitate.