Comparative study on corrosion behavior of as-cast and extruded Mg−5Y−7Gd−1Nd−0.5Zr alloy in 5% NaCl aqueous solution
(1. State Key Laboratory for Fabrication and Processing of Nonferrous Metals,
Beijing General Research Institute for Non-ferrous Metals, Beijing 100088, China;
2. Institute of Technology, Beijing North Vehicle Group Corporation, Beijing 100072, China;
3. Beijing Engineering Research Center for Advanced Manufacturing and Evaluation of Special Vehicle Parts,
Beijing 100072, China)
Beijing General Research Institute for Non-ferrous Metals, Beijing 100088, China;
2. Institute of Technology, Beijing North Vehicle Group Corporation, Beijing 100072, China;
3. Beijing Engineering Research Center for Advanced Manufacturing and Evaluation of Special Vehicle Parts,
Beijing 100072, China)
Abstract: The corrosion behaviours of Mg−5Y−7Gd−1Nd−0.5Zr magnesium alloys prepared by as-casting and extrusion were investigated in 5% NaCl aqueous solution by immersion and electrochemical tests. The microstructure indicates the mean grain size of 15 μm for the extruded and 100 μm for the as-cast Mg−5Y−7Gd−1Nd−0.5Zr magnesium alloys. The corrosion morphology of as-cast sample shows pitting corrosion and little filiform corrosion, but that of the extruded sample shows pitting corrosion at the initial stage. The corrosion rate of extruded sample is higher than that of as-cast Mg−5Y−7Gd−1Nd−0.5Zr alloy according to the immersion test. The second phases containing RE acting as cathodes improve the corrosion properties. The corrosion potentials of as-cast and extruded Mg−5Y−7Gd−1Nd−0.5Zr alloys are −1.658 V and −1.591 V, respectively. The origins of the distinctive corrosion behavior of as-cast and extruded Mg−5Y−7Gd−1Nd−0.5Zr Mg alloys were discussed.
Key words: Mg−5Y−7Gd−1Nd−0.5Zr magnesium alloy; corrosion morphology; polarization curve