Corrosion and protection of magnesium alloys
YU Gang, LIU Yue-long, LI Ying, YE Li-yuan, GUO Xiao-hua, ZHAO Liang (College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China)
Corrosion principle, corrosion types and effects of alloying elements in Mg alloys are introduced. The conventional processes of chemical conversion film, anode oxidation, micro-arch oxidation and electroless plating, and effect of rapid solidification as well as surface modification on corrosion resistance of magnesium alloys are reviewed. Mg alloys are apt to suffer from general, galvanic, pitting, SCC and high temperature oxidation. Approaches toward overcoming corrosion problems are: 1) developing new alloys to increase their thermodynamic stability, RE alloys are promising in resistance to high temperature oxidation; 2) the treatment surface of SiO 2, Al 2O 3 rich coatings and containing SiC, F - or amorphous coatings to improve the corrosion and wearing resistance; 3) improvement of the processes, such as rapid solidification and laser annealing, not only excellent mechanical products of Mg alloys are gained by these processes, but also nano-structural coatings on surface are produced to increase the resistance to corrosion and wear. The new developments of surface treatment are to investigate the processes of nano-structural or glassy coatings on the surface of Mg alloys.