Effect Of 8-Hydroxyquinoline On Corrosion Resistance Of Vanadate/SDBS Conversion Coating On Magnesium Alloy Surface

Magnesium alloy has strong electromagnetic shielding properties,good thermal conductivity and casting properties,and is widely used in national defense,transportation and other fields,However,magnesium alloy products are prone to corrosion in the application process.The traditional chromate conversion coating technology is widely used in the industry for the anticorrosion technology of magnesium alloy,which has strong anticorrosion performance and low cost.But chromate,which is carcinogenic,seriously harm to ecological environment and human health,has been banned all over the world.Therefore,it is of great industrial value to research the chromium free corrosion protection technology for magnesium alloys.Based on the Vanadate/Sodium Dodecylbenzene Sulfonate（SDBS）coating formation of the research group,this paper studies the effects of six organic coating-Sodium benzoate,tannic acid,8-hydroxyquinoline（8-hq）,hexamethyltetramine（HMTA）,2-mercaptobenzimidazole,thiourea on the corrosion resistance of Vanadate/SDBS conversion coating on magnesium alloy surface.The coating-forming conditions of the best 8-hydroxyquinoline were further optimized,The research results show that the conversion coating prepared on the surface of Mg alloy has the best corrosion resistance under the conditions of 2.2g/L Na VO₃,SDBS 1.2g/L,0.2g/L 8-HQ,pH3.0,reaction temperature 40℃,reaction time 15min.and the neutral salt spray time increased from 80h to 140h.SEM and EDS analysis results showed that the vanadate/SDBS/8-hq composite conversion coating was uniform,dense,and amorphous,the coating thickness was 3.15μm.The content of element V and elementincreased from 1.44%to 6.97%and from13.86%to 30.64%respectively.The results of FTIR analysis showed that 8-HQ participates in the formation of a coating layer while promoting the formation of a layer of vanadate and SDBS on the surface of the magnesium alloy,so that the corrosion resistance of the film layer is enhanced.Tafel curve and EIS analysis results show that the corrosion potential of the composite coating is shifted by 140m V（from-1.38V to-1.29V）,the corrosion current density is reduced by 92.3%,and the impedance value in the low-frequency region（0.01 Hz）is expanded by 25 times（from 420Ω·cm²to10570Ω·cm²）,and the corrosion resistance is significantly enhanced.