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 Mg(2)Ge 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 Mg(17)Al(12) phase, which changes the phase composition of the alloy and also affects its microstructure, thus affecting its corrosion performance.