Synthesis of Nano Ceramic Epoxy Hybrid Composite Coating on Metallic Substrate for Corrosion Protection

Abstract

In this study, the corrosion protection behavior of fumed SiO2 reinforced epoxy composite coatings applied on steel substrates was evaluated and compared to graphene-epoxy nano-composite coatings. Graphene-epoxy nano-composite coatings provide excellent corrosion protection but the uniform dispersion of graphene in polymer solvent is a challenge. So, the fumed silica was chosen as the reinforcement rather than graphene. Fumed silica was treated with stearic acid and used with epoxy to get hydrophobic and corrosion resistant coatings. The partial carburization of epoxy was carried out to get carbon layer on steel substrate. The epoxy was cured at various temperatures (200, 250 and 300 °C) to see its effect on hydrophobicity and corrosion behavior of the composite coatings. Presence of different functional groups of modified silica and epoxy was confirmed by FTIR ATR. Coating prepared from this material was evaluated microscopically with respect to structure, uniformity and interface with optical microscope. Polarization effect of coatings was studied by potentiodynamic polarization method. Coating thickness was measured by an Elcometer gauge, and these were checked by the micrographs at 50, 200 and 1000x. E250 (60% epoxy + 6% Silica) showed corrosion rate of 0.017mpy much lower than uncoated steel substrate (2.612mpy). Contact angles for npc200 (neat partially carburized epoxy cured at 200°), 4Si70 (60% epoxy+4% Silica cured at 70°), 6Si300 (60% epoxy+6% Silica cured at 300°) and 6Si250 (60% epoxy+6% Silica cured at 250°) were 90°, 89.5°, 72.5° , 97.5° respectively. So, it was proved that partially carburized epoxy coating with 6% modified silica cured at 250 °C was more corrosion resistant and hydrophobic in nature.