Influence of amino functionalised POSS additive on the corrosion properties of (3-glycidoxypropyl)trimethoxysilane coatings on AA 2024 alloy

Abstract

The influence of the addition of a mixture of POSS compounds substituted equally by 3-aminopropyl and isobutyl groups (AP 4IB 4 POSS) on sol–gel coatings prepared from (3-glycidoxypropyl)trimethoxysilane (GPTMS) was evaluated from the point of view of their anticorrosion properties. AP 4IB 4 POSS belong to a group of polyhedral oligomeric silsesquioxanes and their functionalisation with amino groups enables cross-linking with the epoxy groups of GPTMS. Additionally, GPTMS molecules react among themselves through hydrolysis and condensation processes of trimethoxysilane groups when catalysed by 0.1 M KF. The results of the Raman and IR measurements revealed that a molar ratio of GPTMS:H 2O = 1:3 is more beneficial than a molar ratio of 1:1.5 for the preparation of sol–gel coatings. The anticorrosion properties of the mixed GPTMS/POSS coatings deposited on AA 2024 aluminium alloy were tested using potentiodynamic electrochemical measurements and a salt-spray chamber test. It was found that the mixed GPTMS/POSS coatings showed improved corrosion protective properties vs. either pure GPTMS or POSS coatings.