Electroplating of Al on Mg alloy in a dimethyl sulfone–aluminum chloride bath

• Al coating was electrodeposited on AZ61 Mg alloy in a (CH3)2SO2–AlCl3 bath.
• The adhesion of the Al coating was measured using a pull-off test.
• Zincate treatment improved the adhesion of the Al coating.
• The Al coating effectively prevented the Mg alloy from rapid corrosion.

Electroplating of Al on a Mg alloy using a dimethyl sulfone–aluminum chloride bath was studied. Although dense and uniform Al films were electrodeposited on the Mg alloy from the bath at 110 °C, the adhesion of the Al film was poor when the electrodeposition was carried out directly onto the bare alloy. Subjecting the Mg alloy to zincate pretreatment resulted in Al films with good adhesion. The adhesion strength of the Al films was measured using a pull-off test. The fractured interface was observed with SEM–EDX, which revealed that the Mg alloy substrate reacted with the bath before the electrodeposition of Al started. The reaction products formed on the substrate were detrimental to the adhesion of the electrodeposited Al film. Polarization curves measured for the Al-coated Mg alloy in a 3.5 wt.% NaCl solution at room temperature (25 °C) showed that the Al film electrodeposited from the DMSO2–AlCl3 bath can effectively prevent the Mg alloy from rapid corrosion.