A COMPARATIVE-STUDY ON THE PASSIVATION AND LOCALIZED CORROSION OF ALPHA-BRASS AND BETA-BRASS IN BORATE BUFFER SOLUTIONS CONTAINING SODIUM-CHLORIDE .2. X-RAY PHOTOELECTRON AND AUGER-ELECTRON SPECTROSCOPY DATA

The composition of corrosion layers formed on alpha-, beta- and (alpha + beta)-brass anodized in the passive region in borate-boric acid buffer and 0.5 M NaCl + borate-boric acid buffer (pH 9) was studied comparatively by X-ray photo-electron and Anger electron spectroscopy. Passivation of brass in both solutions involves the formation of a complex passive layer consisting of ZnO and Cu2O. In both solutions, the ZnO electroformation results in a dezincification so that a thin Cu rich layer is formed at the alloy/metal oxide interface. Passive layer composition and dezincification of the alloy surface explain the localized corrosion resistance of brass as compared to polycrystalline Cu and Zn.