Effect Of Alloy Elements On Corrosion Behavior Of Magnesium Alloy

At present,the development of lightweight products has become the mainstream of the times,and magnesium and its alloys have received widespread attention and studied for their low density,light mass,high specific strength,high modulus of elasticity,good damping performance and excellent casting performance.Nevertheless,one of the main obstacles hindering the development and wider use of magnesium alloys is the poor corrosion resistance and complex dissolution behavior of Mg.Therefore,it is of great significance to clarify the corrosion mechanism of magnesium and its alloys to design corrosion-resistant magnesium alloys and expand the application scope of magnesium alloys.This paper takes the Mg-x In(x=0.5,1,1.5 wt.%),Mg-x Zn(x=1,1.5,2 wt.%),and Mg-Sn(x=1.5,2,5wt.%)alloys as the research object.Potentiodynamic polarization was used to analyze the influence of different alloying elements on the corrosion behavior of magnesium alloys.The electrochemical corrosion of magnesium alloys was quantitatively analyzed by hydrogen evolution collection during galvanostatic polarization experiments.The microtopography of magnesium alloys after anodic galvanostatic polarization were analyzed by scanning electron microscopy,and the influence of alloying elements on the NDE of magnesium alloys was quantitatively analyzed with Tafel extrapolation method.The following main conclusions were obtained:(1)The analysis of the potentiodynamic polarization results showd that the addition of In to Mg can improved the corrosion resistance of magnesium alloys in 0.1 M Na Cl solution,and with the increase of In content,the corrosion resistance gradually improves,and the solid-solution Mg-1.5In alloy had the best corrosion resistance.The solid solution of Zn in the Mg can improve the corrosion resistance of magnesium alloys in 0.1 M Na Cl solution to a certain extent,and the solid-solution Mg-1.5Zn alloy had the best corrosion resistance,but the corrosion resistance was not as good as the solid-solution Mg-In alloy.With the increased of the Sn content in the Mg matrix,the corrosion resistance of the solid-solution Mg-Sn alloy gradually decreased.Among them,the Mg-1.5Sn alloy had the best corrosion resistance,but it was not as good as the solid-solution Mg-1.5In alloy and the solid-solution Mg-1.5Zn alloy.(2)The solid-solution Mg-In,Mg-Zn,and Mg-Sn alloys all had strong anomalous hydrogen evolution during the anodic galvanostatic polarization.By calculating the exchange current density of the hydrogen evolution reaction(i_0,H,Mg),it can be seen that the hydrogen evolution rate of the magnesium alloy increase with the increase of the exchange current density.The exchange current density was related to the catalytic activity of the alloy surface.Therefore,it can be concluded that the increase in the catalytic activity of the alloy surface during the anodic polarization is the cause of the NDE of the magnesium alloy.By analyzing the coverage of corrosion products on the alloys surface and the surface cathode kinetics after corrosion,it can be known that corrosion products are not the main reason for the NDE of magnesium alloys.(3)For Mg-In alloys,the rate of hydrogen evolution measured under anodic galvanostatic polarization showed a clear dependence on the concentration of In in the Mg alloy.The anomalous rate of HE decreased with increased In content,and the solid-solution Mg-1.5In alloy had the lowest rate.The i_0,H,Mg of the magnesium alloy gradually decreased with the increase of In content.Combined with the increased catalytic activity mechanism,it showd that the In element can inhibit the NDE.The research results of Mg-Zn alloys also showd that with the increase of Zn content,the NDE of magnesium alloy is suppressed,and the mechanism was similar to that of Mg-In alloys.For Mg-Sn alloys,with the increased of Sn content,the i_0,H,Mg of the magnesium alloy gradually increased.Indicating that the catalytic activity of the alloy surface increases,and the ability to suppress the negative difference effect of the magnesium alloy decreases.(4)In the whole anodic current densites range,the hydrogen evolution reaction exchange current density of the solid-solution Mg-In alloy was the lowest,followed by the solid-solution Mg-Zn alloy,and the solid-solution Mg-Sn alloy was the highest.The ability to suppress the NDE of magnesium alloys increased in the order of Mg-Sn<Mg-Zn<Mg-In.The exchange current density of the alloy elements added to the magnesium alloy can affect the negative difference effect of the magnesium alloy.The lower the exchange current density of the alloy element,the stronger its ability to inhibit the negative difference effect of the magnesium alloy.