Electrochemical Behavior Of Cerium And Lanthanum Mischmetal On Corrosion Resistance Of AM60B Magnesium Alloy

Magnesium alloy is widely used in information industry, military weapon, auto parts, chemical industry and energy engineering, etc, and it is developing rapidly.The standard potential of magnesium is -2.37 V, which is more negative than other metal materials and easy to cause magnesium as sacrificial anode and suffer from corrosion. As alkali metals of ⅡA family, chemical properties of magnesium is active. MgO thin film can be easily created on the surface in the air,but not dense,which is unable to reduce the oxidation process effectively.So the poor performance of magnesium corrosion become one of the important factors that restrict its development.In this paper, through adding mixed rare earth Ce and La into AM60B magnesium alloy, electrochemical behavior of rare earth magnesium alloy (hereinafter referred to as AM60B-MM) are studied in NaCl solution. The results showed that corrosion weight gain of AM60B-MM and AM60B magnesium alloy in NaCl solution increases as the raise of test temperature and concentration of NaCl solution.corrosion weight gain of AM60B-MM is 5.949 mg/cm2, less than 12.975 mg/cm2 of AM60B in 25℃ 3.5% NaCl solution. Electrochemical testing results showed that AM60B-MM corrosion potential is moved right, and anodic polarization current density decreased;The 0-Mg17Al12 organization of AM60B- MM alloy change to discontinuous state and the distribution of particle dispersion, and a needle of rare earth phase and CeO2 & Mg17La12 appear in the corrosion products, which have the effect of refining grain, make magnesium alloy oxide film more compact, and improves the corrosion resistance of magnesium alloys.25℃ alkaline hydrogen evolution results in 3.5% NaCl solution shows that, stable hydrogen evolution corrosion current density of AM60B- MM magnesium alloy is lower than that of AM60B magnesium alloy. After adding mixed rare earth Ce and La,corrosion potential of AM60B-MM magnesium alloy is right moved, anodic polarization current density is reduced, the capacitive reactance arc and low-frequency impedance modulus value increases,and the phase Angle increases, which form a shielding layer of high resistance and low capacitance,and electrochemical performance was improved.XRD spectroscopy analysis of corrosion products found that CeO2 and La2O3 composite oxide film appear in AM60B-MM magnesium alloy.Crevice corrosion weight gain of AM60B-MM and AM60B magnesium alloy immersed after 30d in 25℃0.35% NaCl solution were 24.832 mg/cm2 and 24.832 mg/cm2, that means crevice corrosion resistance of AM60B-MM magnesium alloys is improved.