The Influence Of Li, Zn And Al On The Corrosion Property Of Magnesium Alloys

At present, the research on corrosion property of Mg alloys mainly concentrates in two aspects: one is the alloying of Mg alloys, which can improve the corrosion resistance of Mg alloys by modifications of microstructure. The other is the surface protection, which is the most extensive research direction to improve corrosion resistance of Mg alloys. However, the long term of corrosion property of Mg alloys is rarely researched.In this paper, pure Mg and Mg-Li alloys with different lithium contents were immersed in 3.5% NaCl solution for 72 h, the evolutions of corrosion rate, corrosion electrochemical parameters, morphology and corrosion products were characterized, and the effect of lithium content on the corrosion behavior of magnesium lithium alloy in the long-term corrosion was analyzed. Besides, the effects of different alloying elements, Al, Zn, Li on the corrosion property of magnesium alloys in the long-term corrosion were analyzed and summarized. The content of the alloying elements is chosen as 3 wt. %.Through the results of hydrogen evolution, corrosion weightlessness, Tafel polarization curve and impedance spectrum,it is found that the corrosion performance of Mg-Li alloys is better than pure magnesium after long-time corrosion. Among three kinds of Mg-Li alloys,Mg-3Li, Mg-9Li and Mg-12Li, the corrosion resistance of Mg-3Li is best, followed by Mg-12Li, the corrosion resistance of Mg-9Li is the worst. During the corrosion, duplex Mg-9Li presents the typical filiform corrosion morphology; single-phase Mg-3 Li and Mg-12Li present localized pitting corrosion and gradually evolve into comprehensive corrosion on the surface of the alloys. Corrosion products of Mg-Li alloys are different from pure magnesium, in Mg-Li alloys, besides Mg(OH)2 and MgO, the corrosion products contain LiOH.Compared with the corrosion characterizations of Mg-3Li, Mg-3Zn, Mg-3A1, it is found that, after long term corrosion, Mg-3 Li possesses the best corrosion resistance and corrosion resistance of Mg-3 A1 is the worst.