Al diffusion coating on Mg alloy by a surface nanocrystallization enhanced CVD process

Surface nanocrystallization by mechanical attrition was used to enhance the chemical vapor deposition process. An aluminum (Al) diffusion coating was produced on AZ91 Mg alloy surface. This process was conducted at a relatively low temperature (400°C) for a short time of 120 min. The results indicated that a continuous and dense Mg₁₇Al₁₂ intermetallic coating with a thickness of ～8 μm formed on the Mg alloy substrate. Almost no corrosion was observed after the coated samples were immersed in 3 wt % NaCl solution for 6 h, reflecting a relatively good corrosion resistance. The formation mechanism of the Al diffusion coating is discussed based on the experimental results.