SVET Study of Galvanic Corrosion of Al/Mg₂Si Couple in Aqueous Solutions at Different pH

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