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

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