Influence of intermetallic Al-Mn particles on in-situ steam Mg-Al-LDH coating on AZ31 magnesium alloy
(1. Corrosion Laboratory for Light Metals, College of Materials Science and Engineering, Shandong University of Science and Technology, Qingdao 266590, China;
2. School of Engineering, University of Newcastle, Callaghan, New South Wales 2308, Australia;
3. College of Science and Engineering, James Cook University, Townsville, Queensland 4811, 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. School of Engineering, University of Newcastle, Callaghan, New South Wales 2308, Australia;
3. College of Science and Engineering, James Cook University, Townsville, Queensland 4811, 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 influence of intermetallic Al-Mn particles on the corrosion behavior of in-situ formed Mg-Al layered double hydroxide (Mg-Al-CO32--LDH) steam coating on AZ31 Mg alloy was investigated. The alloy was pretreated with H3PO4, HCl, HNO3 or citric acid (CA), followed by hydrothermal treatment, for the fabrication of Mg-Al-LDH coating. The microstructure, composition and corrosion resistance of the coated samples were investigated. The results showed that the surface area fraction of Al-Mn phase exposed on the surface of the alloy was significantly increased after CA pretreatment, which promotes the growth of the Mg-Al-LDH steam coating. Further, the LDH-coated alloy pretreated with CA possessed the most compact surface and the maximum coating thickness among all the coatings. The corrosion current density of the coated alloy was decreased by three orders of magnitude as compared to that of the bare alloy.
Key words: magnesium alloy; acid pretreatment; layered double hydroxide; intermetallic particles; steam coating; corrosion resistance