The anodic polarization curve of copper in borate buffer solution at pH 11 shows two anodic current peaks at -0.26V(Paa1)and -0.03V(Pa2)and a passive region with a small hump at a more positive potential. It is found from the result of a channel flow electrode that Pa1corresponds to the formation of Cu2O, while Pa2seems to be related with the formation of Cu(OH)2. The presence of carbonate ion hinders protective Cu(OH)2passive layer formation. The addition of chloride ion (>0.5 mol/l) causes pitting corrosion at a potential close to oxygen evolution. The stability of the passive film in alkaline solution is lowered by the presence of carbonate or chloride ion. The anodic polarization curve obtained in concentrated carbonate-chloride solution (>1mol/l) at pH11 shows two Tafel regions, the slope of which has 60 and 40 mV/decade, proceeding Pa1and Pa2, respectively. Active dissolution model in both Tafel regions have been proposed. © 1990.
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