| As a light metal material,magnesium alloy is suitable for application in many fields.However,due to its own defects,its extensive use is greatly reduced,and the poor corrosion resistance of magnesium alloys is the primary factor.Electrodepositing aluminum coating on its surface is an effective method to improve the defects of magnesium alloy itself without adding too much weight.This article uses 1-butyl-3-methylimidazole chloride salt and anhydrous Al Cl3 prepared ionic liquid（BMIC-Al Cl3）as the electrolyte to explore the two-way pulsed electrical The influence of the process parameters of the aluminum coating and the post-treatment heating time on the performance of the aluminum coating.Explore the influence of direct current electrodeposition at different potentials on the corrosion resistance,surface morphology,surface element distribution and porosity of Al coatings.The experimental results show that with the increase of the electrodeposition potential,the self-corrosion current density of the Al coating gradually decreases,and the self-corrosion potential gradually increases;the particles deposited by the Al coating become larger and the coating distribution becomes more and more uniform;The porosity showed a downward trend.At 2 V electrodeposition potential,the self-corrosion current density is1.9×10-5 A·cm-2,the self-corrosion potential is-1.476 V,the aluminum atom content of the Al coating is 87.14%,and the porosity of the Al coating is 23.86%.Explore the effects of bidirectional pulse electrodeposition on the corrosion resistance,surface morphology,surface element distribution and porosity of Al coatings.Design a5-factor 5-level orthogonal experiment and two sets of additional experiments under special circumstances,and the best process parameters are:positive pulse duty cycle d1=70%,negative pulse duty cycle d2=70%,positive and negative pulse width Ratio D=1,period T=20ms,positive pulse voltage U1=2 V,negative pulse voltage U2=0.7 V.The primary and secondary relationship of the five influencing factors on the corrosion resistance of the coating is:d1>U2>d2>T>D.The self-corrosion potential of the coating obtained under these conditions is-0.244 V,the self-corrosion current density is 2.716×10-7 A·cm-2,the aluminum atom content of the coating surface is 94.41%,and the porosity of the coating is 10.93%.The results of the two additional experiments show that as the ratio of the positive and negative pulse width D decreases,the self-corrosion current density increases,the self-corrosion potential negatively shifts,the aluminum content of the coating surface decreases,and the porosity of the coating increases;with the negative pulse voltage U2 The increase in self-corrosion current density,the negative shift of self-corrosion potential,the decrease of aluminum content on the surface of the coating,and the increase of the porosity of the coating.Taking the best process parameters as the electrodeposition process conditions,the Al coating on the magnesium substrate was post-heated at 400℃.The experimental results show that as the post-treatment time increases,the self-corrosion potential gradually shifts positively,and the self-corrosion current density gradually decreases;the aluminum content on the surface of the Al coating continues to increase;the porosity of the aluminum coating shows a downward trend.When the heating time is 120 h,the self-corrosion potential of the aluminum coating on the magnesium alloy surface is-0.185 V;the self-corrosion current density is 4.997×10-8 A·cm-2;the percentage of Al atoms on the aluminum coating is 99.18%;The porosity of the aluminum coating is 4.84%. |
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