Evaluation of anti-corrosive properties of epoxidized rubber and siloxane hybrid coatings

Abstract

Elastomeric hybrid films were produced from the epoxidized nitrile rubber with the 3-glycidyloxypropyl-trimethoxysilane (GPTMS) inorganic precursor by the sol–gel process. There were no significant changes in the thermal properties of hybrids in relation to pure epoxidized rubber. The degree of swelling decreased while the mechanical resistance increased with increasing GPTMS content. The sol–gel process was performed on metal plates, which were then subjected to a corrosion process by immersion in NaCl solution and evaluated by Electrochemical Impedance Spectroscopy. The resistance and the capacitance values of the nitrile rubber coating are 8.8 × 10³Ωcm² and 1.9 × 10⁻⁴Fcm⁻², whereas for the hybrid with 38phr of GPTMS the values are 2.3 × 10⁶Ωcm² and 15.8 × 10⁻¹⁰Fcm⁻², respectively, indicating higher cross-link density, less electrolyte absorption, less degradation, greater adherence to the metal surface via silane groups and, consequently, better corrosion protection achieved by the hybrid films.