Surface modification of magnesium alloys by deposition coating

In order to improve corrosion resistance in magnesium alloys, surface modification was attempted by applying a vapor deposition technique. Evaporation source, 3N-Mg, and substrate plates for deposition, AZ31 magnesium alloy, were put into a vacuum furnace with five heating zones. The evaporation source was heated at about 873 to 1073 K, while the substrates plates were held at temperatures in the range of about 470 to 660 K in vacuo for 3.6 to 9.0 ks. Magnesium particles with about 5 to 50 mum in diameter, which depended on the heating temperatures of the substrate, were formed to cover the surface of the substrate plate with AZ31. Corrosion resistance of the deposition coated AZ31 specimen was evaluated in salt immersion tests using 1% NaCl solution. Weight loss in the coated specimen in the 1% NaCl solution was smaller than uncoated AZ31 alloy by about a factor of ten. The present technique intrinsically has purification reaction, which results in improving the corrosion resistance.