Study On AZ91D Magnesium Alloy Surface Of Polyimide Coating Preparation And Corrosion Resistance

Select thermosetting polyimide?PI?as AZ91D magnesium alloy coating material,in order to improve the bonding strength of coating and the magnesium,Magnesium alloy need to be treated by silane before coating polyimide.The polyimide characteristic functional groups were characterized by FTIR;The analysis of the thermal stability of the polyimide by Using differential scanning heat meter?DSC?and thermogravimetric analyzer?TG?;The film morphology observation analysis was carried out by means of metallographic microscope,scanning electron microscope?SEM?;According to related national standards the adhesion strength of the film layer and the substrate by using cross experiment and tape the experiment method of combining the testing;The corrosion resistance of film layer and substrate by using salt water immersion text.This topic selectised KH-560,epoxy silane,theoretically it not only have good ability to combine with metal,also particularly effective for the combination of the polyimide.After treated with silane,the surface of magnesium alloy coated by polyamide acid?PAA?,then after heat treatment we can get polyimide coating.For the preparation of 5 kinds of coating:magnesium/silane/PAA,magnesium,magnesium/PI,magnesium/silane/PAA,mg/silane/PI bond,the corrosion resistance were compared.And discuss the adhesive power and corrosion resistance of different functional groups and solid content of different polyimide coating.Conclusion:5 kinds of coating corrosion resistance strength:silane/PAA>silane>PI>silane/PI>PAA,the solid content of 15%of polyimide film has the best corrosion resistance,polyimide film containing flexible group has more corrosion resistance.Analyzed with flexible group-C?CH₂?₂-ODPA/BAPP type polyimide in coating application performance,and compared with traditional thermosetting type PMDA/ODA polyimide.Experiments show that 15%solids or 20%solids contain flexible group BAPP type and the corrosion resistance of polyimide was obviously higher than that of PMDA type polyimide.Conclusion:polyimide flexible groups can improve the molecular chain of free rotation,the degree of distortion in the space,effectively reduce the molecular chain rigidity,improve the bond strength of the coating and matrix.