Fabrication of Al coating for corrosion protection of Mg-Zn-Al-Sn-Mn alloy based on cold spraying process
(Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061, China)
Abstract: Al coating was fabricated on the surface of Mg-Zn-Al-Sn-Mn alloy by cold spraying process to enhance its corrosion resistance. The effects of temperature and pressure of working gas on the microstructure and corrosion behaviors of Al coating were investigated. The results show that as gas temperature and pressure increase, the densification and thickness of Al coating obviously increase. High gas temperature declines the critical velocity of powder deposition and increases the deposition efficiency. High gas pressure not only improves the quality of mechanical bonding, but also provides strong tamping effect on the deposited coating. Due to the reduction of porosity, the corrosion resistance of Al coating is improved with the increase of gas temperature and pressure. The corrosion products of Al(OH)3 and Al2O3 can block the pores in Al coating and act as physical barriers to corrosion, which effectively protects Mg alloy from being corroded.
Key words: cold spraying; Mg alloy; Al coating; corrosion resistance; microstructure