Corrosion Behavior of the As-Cast and As-Solid Solution Mg-Al-Ge Alloy

The corrosion behavior of Mg-3Al-xGe (x = 1, 3, 5) alloy in as-cast and as-solid was investigated by virtue of microstructure, corrosion morphology observation, and electrochemical measurement. Among the as-cast alloys, the corrosion rate of Mg-3Al-1Ge with a discontinuous bar-morphology was the highest, which was 101.7 mm·a^-1; the corrosion rate of Mg-3Al-3Ge with a continuous network distribution was the lowest, which was 23.1 mm·a^-1; and the corrosion rate of Mg-3Al-5Ge of Ge-enriched phase with sporadic distribution was in-between, which was 63.9 mm·a^-1. It is suggested that the morphology of the Mg₂Ge phase changes with a change in Ge content, which affects the corrosion performance of the alloy. After solid solution treatment, the corrosion rate of the corresponding solid solution alloy increased-Mg-3Al-1Ge to 140.5 mm·a^-1, Mg-3Al-3Ge to 52.9 mm·a^-1, and Mg-3Al-5Ge to 87.3 mm·a^-1, respectively. After investigation of the microstructure, it can be suggested that solid solution treatment dissolves the Mg₁₇Al₁₂ phase, which changes the phase composition of the alloy and also affects its microstructure, thus affecting its corrosion performance.