Novel hybrid epoxy silicone materials as efficient anticorrosive coatings for mild steel

Abstract

Novel hybrid-sol–gel materials (C1–C5) based on silica–epoxy composite resins were successfully prepared by coupling different aminosilanes with DER736 epoxy resin, followed by an in situ sol–gel process, and finally introducing the urethane moieties to the final coatings. This research has emphasized the effect of changing the type of aminosilane on the properties of the prepared hybrid coatings. Three different aminosilanes were examined and their reaction parameters with the epoxy and the trialkoxysilanes were carefully optimized in order to avoid fast gelation and to obtain the desired properties of the hybrid coatings. The prepared organic–inorganic hybrid coatings were loaded and cured on mild steel panels and characterized for FTIR, NMR, TGA, water contact angles (WCA), nanoindentation hardness, pull-off adhesion, SEM, EIS and polarization studies. The results revealed that the coatings prepared from the trialkoxysilanes APTMS and MTMS (C4) demonstrate the best mechanical, anticorrosion and adhesion properties on mild steel substrates as compared to all other coatings in a 3.5 wt% NaCl medium. Electrochemical impedance spectroscopy (EIS) results indicated a corrosion resistance value for this coating in the range of 10⁶ Ω cm² after 10 days of continuous immersion in the saline medium. The SEM observations suggest that coatings produced from the other aminosilanes, APT-PDMS and APM–DMS are inhomogeneous and have some defects which have ultimately affected their barrier protection properties.