Surface treatment of magnesium alloy castings for corrosion protection

摘要

A method is disclosed for improving the corrosion behavior of cast magnesium alloy articles in which the magnesium alloy comprises an average composition of more than about 5 per cent by weight of aluminum. A microstructure with regions of varying aluminum content is developed during solidification. The microstructure comprises magnesium-rich grains generally surrounded by an aluminum-enriched phase on the boundaries between adjacent grains. The magnesium-rich grain interiors are then selectively chemically or electrochemically attacked to leave a more corrosion resistant aluminum-enriched surface on the articles. The corrosion resistance of the articles may be further enhanced by one or more of anodizing, aluminizing or painting the corrosion-resistant aluminum-enriched surface.