Corrosion resistance of rapidly formed in-situ steam Mg-Al LDH coating on AM50 Mg alloy pretreated with oxalic acid
(1. Corrosion Laboratory for Light Metals, College of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, China;
2. State Key Laboratory of Nonferrous Metals and Processes, GRINM Group Co., Ltd., Beijing 100088, China;
3. School of Engineering, University of Newcastle, Callaghan, New South Wales, 2308, Australia;
4. College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, China;
5. School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002, China)
2. State Key Laboratory of Nonferrous Metals and Processes, GRINM Group Co., Ltd., Beijing 100088, China;
3. School of Engineering, University of Newcastle, Callaghan, New South Wales, 2308, Australia;
4. College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, China;
5. School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002, China)
Abstract: The effect of oxalic acid (OA) etching on the formation mechanism and corrosion performance of in-situ steam Mg-Al layered double hydroxide (LDH) coatings on AM50 Mg alloy was investigated by exposing the intermetallic compounds (β-Mg17Al12 and AlMn) on the surface of the alloy. The results demonstrated that the presence of OA led to an increased fraction of intermetallic compounds on the Mg substrate. Mg-Al LDH nucleated and grew around the Al-Mn phase. The best corrosion resistance of LDH coating was obtained with the maximum thickness at a pickling time of 45 s, and the corrosion current density was reduced by three orders of magnitude compared to the substrate. Finally, the formation mechanism of Mg-Al LDH coating on AM50 Mg alloy was proposed.
Key words: magnesium alloy; oxalic acid; intermetallic compound; steam coating; layered double hydroxide; corrosion resistance