Improvement of Al coating adhesive strength on the AZ91D magnesium alloy electrodeposited from ionic liquid

Adhesive strength of Al coatings electrodeposited on AZ91D in aluminum chloride/1-ethyl-3-methylimidazolium chloride was improved by the development of a zincate pretreatment and optimized current pulse electrodeposition method. A dense Zn layer was deposited on both the α- and β-phase surfaces of AZ91D substrate pre-treated in a Cu2+ added activation bath prior to the zincate process. On this zincated substrate an Al coating was electrodeposited by bipolar current pulse polarization and the adhesive strength of the Al coating to the substrate was better than 11 MPa. The Al coating obtained under the optimal condition also showed good corrosion resistance in 3.5 wt.% NaCl solutions.