Bonding an corrosion rotection mechanisms of lambda-APS and BTSE silane films on aluminum substrates

摘要

Films of lambda-aminopropyltriethoxysilane(lambda-APS),1,2-bis[triethoxysilyl]ethane(BTSE)and their mixtures absorbed onto pure aluminum from aqueous solutiosn were characterized by means of ellipsometry,infrared spectroscopy(IR) and X-ray photoelectron spectroscopy(xPS).It was foudn that after hydrolysis in water the silnes werereadily adsorbed onto aluminum oxide surfaces initially forming hhydrogne bonds.Upon curign,such bonds arereplaced bymetallosiloxane bonds,Si-O-Al.The remaining silanol groups in the film condense and form Si-O-Si bonds.As the Si-O-Al bonds are known to hydrolyze,the corrosion protecton is related to the hydrophobicity of the siloxane films formed on teh metal substrate.BTSE films re acidic as they ocntain free silanol groups,therefore these are compatible iwth some paints but not with others.Electrochemcial impedance spectroscopy (EIS) results,salt spray test results and filiform corrosion test results showed that some silane treatments,such as two-step lambda-APS/BTSe and STSe only,provided better corrosion protectionon aluminum substrates as compared with a chromate treatment.mechanisms of adhesion and corrosion protection f these silane films on aluminum substratesare proposed.