SVET Study of Galvanic Corrosion of Al/Mg 2 Si Couple in Aqueous Solutions at Different pH

Abstract

The galvanic corrosion behavior between pure Al and synthesized bulk Mg2Si in 0.01 M NaCl solution at different pH values has been investigated by the scanning vibrating electrode technique (SVET). At pH 2, bulk Mg2Si actively dissolves and it acts as an anode. With the increase of exposure time, the anodic activity of Mg2Si decreases drastically and eventually anodic activity appears on Al surface. In alkaline solution, Mg2Si phase always acts as the cathode. The preferential dissolution of Mg and enrichment of Si found by energy dispersive X-ray spectroscopy are responsible for the observed anodic activity decay of Mg2Si in acidic solution. At pH 6, the galvanic corrosion current of Al/Mg2Si couple is much less than those at pH 2 and pH 13, and Mg2Si mainly undergoes self-dissolution. These results indicate that the dealloying of binary Mg2Si phase depends on the solution pH value and corrosion time, which subsequently have a great influence on the galvanic corrosion current of Al/Mg2Si couple.