ELECTROCHEMICAL PASSIVATION OF COPPER-ALUMINUM SILVER ALLOY IN SODIUM-HYDROXIDE SOLUTION

The effect of consecutive cyclic polarization of a new heat treated and mechanically polished Cu-Al-Ag alloy of entirely new composition with a high aluminium content on the surface microstructure has been studied using scanning electron microscopy and X-ray diffractometry. The electrochemical behaviour of this alloy in 0.5 m NaOH has been studied using cyclic voltammetry and impedance measurements. Repetitive triangular sweeps (RTPS) potential scans between hydrogen and oxygen evolution in alkaline media lead to preferential dissolution of the aluminium. The steady state I-E profile of the alloy after the RTPS pretreatment indicates surface dealloying of aluminium due to its preferential dissolution, and shows a characteristic similar to that for high purity copper and silver.