Modified bis-(3-(3-(3-triethoxysilyl)propyl)thioureido)propyl terminated poly(dimethylsiloxane)/POSS protective coatings on AA 2024

Abstract The aim of this work was to investigate the protective behaviour of bis-(3-(3-(3-triethoxysilyl)propyl)thioureido)propyl terminated polydimethylsiloxane (PDMSTU) pre-treatment coatings on the AA 2024 aluminium alloy. The silane solution was modified by the addition of bis-([3-(triethoxysilyl)propyl]tetrasulphide) (BTESPT) and trisilanol-heptaisooctyl-POSS (TS-iOc 7 -POSS) in order to introduce better crosslinking and improved mechanical and electrochemical stability in the silane primer coating. The corrosion behaviour of the protected AA 2024 alloy was studied during immersion in 0.5 M NaCl solution, using potentiodynamic polarisation measurements and eventual structural changes were followed using in situ Raman spectroelectrochemical technique. The electrochemical experiments showed that the presence of BTESPT and TS-iOc 7 -POSS molecules improves the protective behaviour of the silane coating, while Raman imaging was used to determine their distribution in coatings.