Electrodeposition of chemically and mechanically protective Al-coatings on AZ91D Mg alloy

摘要

Electrodeposition of aluminium coatings upon AZ91D in aluminum chloride/1 -ethyl-3-methylimidazo-lium chloride ionic liquid was achieved. Post-plating heat treatment processes compatible with AZ91D solution treatment (420 ℃) and aging treatment (200 ℃) were explored to improve coatings adhesion and hardness, and to maintain corrosion resistance. 420 ℃ treatment produced a β-phase (Mg_(17)Al_(12)) enriched two-phase coating; whilst treatment at 200 ℃ leads to a tri-layer structure, rich in γ-phase (Mg_2Al_3). The 200 ℃ treatment was shown to be most effective for corrosion resistance, eradicating water reduction as the principal cathodic reaction and increasing surface hardness.