Passivation of Pure Copper

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The passivation of pure copper in a synthetic industrial electrolyte containing nickel at 65 ^oC was investigated by Ghali and others. Using potentiostatic and voltammetric techniques Garneau et al. generated a passivating film and determined it to be mostly CuSO₄· 5H₂O by X-ray photoelectron spectroscopy and scanning electron microscopy. Cu₂O was also detected after multiple sweeps using cyclic voltammetry. Jin and Ghali found similar results using chronopotentiometry followed by X-ray induced Auger electron spectroscopy (XAES) . Gauthier, Manzini and Ghali found copper sulfate and copper oxides by SEM and XAES after passivation in linear sweep voltammetry.

These findings coincide with the discussion presented by Kortum on film formation and growth. An oxide coating on metals is predominantly an ion conducting film which forms only after an increase in voltage caused by the formation of a non-conducting film. Therefore, it is believed for pure copper, a CuSO₄· 5H₂O (a non-conducting substance) film forms by precipitation from the saturation of the boundary layer. This results in an increase in potential, which allows the formation of Cu₂O.

Anode Passivation Main Page

Copper Dissolution

Passivation of Impure Copper Anodes

Secondary Phases Within the Anode

Slimes

Non-Slime Impurities

Electrolyte

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