Effect of Aging on Corrosion Resistance of AZ31 Magnesium Alloy

The corrosion resistance of AZ31 magnesium alloy is strongly related to the microstructure, while the corrosion process leads to the production of atomic hydrogen that can penetrate the magnesium lattice and provoke stress corrosion cracking (SCC). The rate of SCC depends on the magnitude of hydrogen diffusion in magnesium and its alloys. In this work, analysis was made of the hydrogen diffusion coefficient and corrosion resistance of AZ31 alloy solubilized at 440 degrees C for 24 h and submitted to aging heat treatment at 220 degrees C for 6 and 12 h. Hydrogen permeation tests showed that aging of the AZ31 alloy did not affect the hydrogen diffusion coefficient (D). The D value found in this work (similar to 5.0.10(-9) m(2) s(-1)) was in accordance with recent data for Mg. Before performing the corrosion resistance tests, the samples were anodized by micro-arc oxidation at ambient or subzero temperature, in order to improve the corrosion resistance. The samples aged for 12 h and anodized at subzero temperature presented the highest incorporation of silicon, the presence of Mg2SiO4, and the highest corrosion resistance in Hank's solution.