The Electrochemical Study Of Magnesium Alloy-rich Coating After Corrosion In Ocean Environment

Anti-corrosion aluminum alloy is wildly used in ships and important military equipment,and it works in ocean environment with high humidity and high temperature and high salinity.But it is easy to lose function for pitting and crevice corrosion at the link and welding parts because of it has a high-activity property.Magnesium-rich coating can provide a better protection for aluminum alloy,but it also has some disadvantages.Mg-rich coating using pure magnesium grain as filler,but pure Mg has a actively chemistry property and low current efficiency.Corrosion is serious that lead to coating with a low life.While magnesium alloy has a stabilized electrochemical property and high current efficiency and long life.Therefore this paper will use the AZ91D magnesium alloy as filler to protect aluminum alloy and make a electrochemical study.The main works and results are as follow:1.The coating with different PVC in resistant to salt spray test shows that the AZ91D-rich with 50%PVC has a better corrosion resistance and has a long lifetime in corrosion environment.In electrochemical impedance spectroscopy(EIS)test shows that the impedance of coating with PVC35%and PVC65%have decreased below 106?·cm2,while the coating with PVC50%also has a high impedance and shows a good corrosion resistance.2.The Mg-rich coating has a compared with magnesium alloy-rich coating with PVC50%in electrochemical study.Corrosion resistance of magnesium alloy-rich coating is better than Mg-rich coating.The impedance of magnesium alloy-rich coating is higher than Mg-rich coating and it is decreased slowly.Pure magnesium coating surface appears so many porous,the pure Mg has occurred corrosion in the junction of aluminum alloy substrate.3.The magnesium alloy-rich coating,which was made of PVC50%with different scratched size in electrochemical study shows that the protective performance of coating is decreased gradually for the scratched size increasing.4.Through the Electrochemical impedance spectroscopy(EIS)testing,studies the magnesium alloy-rich coating failure process.Coating with PVC50%failure is divided into four phases:Before immersion,Coating likes a shielding layer shows a higher impedance.In the early immersion,it is mainly the diffusion process of water molecules and electrolyte.In the medium-term immersion,Magnesium alloy particles is activated,the internal swelling due to initiation of porous.In the late immersion,the corrosive medium permeability reaches a saturation value,and reaches the surface of magnesium alloy substrate,the coating will lose its performance soon.The conclusions can be drawn that magnesium alloy-rich coating has a better corrosion resistance.It has a important strategic significance which in order to further improve the corrosion resistance,the application prospect of aluminum alloy and social sustainable development.