Corrosion tests are described of two magnesium-silver - rare earth metals - zirconium alloys having different nominal rare earth metal contents. The susceptibility to corrosion of these alloys is compared with that of magnesium-zinc-zirconium alloy to DTD.721A. The degree of protection afforded to these alloys by various surface treatments has also been ascertained. Under an intermittent sea-water spray test, the alloys containing silver and rare earth metals corroded more rapidly than the alloy to DTD.721A. Chromate treatment to bath iii of DTD.911 B, supplemented by surface sealing with an epoxy resin and one finishing coat of paint gave protection equal to that of the chromate treatment and three-coat paint scheme of DTD.911B. Greater protection should result from the inclusion of a chromate pigmented undercoat between the sealant and finishing coat.