Corrosion resistance of aluminium alloy pretreated based on bis-sulphur silane with rare earth salt

Pretreatment for the Al alloy based on bis-[triethoxysilylpropyl]tetrasulphide (BTSPS) with Ce(NO₃)₃ is put forward in order to improve corrosion resistance of AA2024-T3 alloy in the present paper. The coating is formed by one step dip coating. The cross-linked pretreated coating on Al alloy is characterised with reflection absorption infrared spectroscopy. The chemical composition and the in depth distribution of different elements present in the coating are analysed by Auger electron spectroscopy. Corrosion resistance and hydrophobicity of pretreated coating on the Al alloy is respectively assessed by salt spray test, electrochemical tests and thermogravimetric analysis. The role of Ce³⁺ ion and sulphur present in one of the BTSPS solutions in the formation of the surface film is discussed. The results show that the one step pretreatment coating of BTSPS with Ce(NO₃)₃ provides excellent corrosion protection with the Al alloy compared with that of BTSPS without Ce(NO₃)₃.