Corrosion protection of steel using epoxy coatings reinforced with FeSO 4 /FeCl 3 and silane-functionalised rice husk nanosilica

Abstract

Adoption of product innovation via development of coatings from solid wastes can boost the socio-economic development of a nation and facilitate climate action by reducing over-reliance on petroleum-based polymers. In this study, corrosion of A36 steel in 1 M HCl solution was protected using epoxy coatings enhanced with FeSO₄/FeCl₃ and silane-functionalised rice husk nanosilica. Inhibition efficiencies of synthesised organic epoxy coatings were evaluated using weight loss and electrochemical methods. At optimum conditions (100 °C, 3 days, 6 wt% and 120 rpm), the enhanced epoxy coating exhibited inhibition efficiency of 98.71%. The corrosion potential (E_corr) and corrosion current density (I_corr) reduced from −0.6 V to −0.44 V; and 1.11 μA/cm² to 0.46 μA/cm², respectively, while the inhibition efficiency increased from 97.64% to 99.02% when the enhancer concentration was increased from 2 wt% to 6 wt%. Impedance spectra revealed an increase in the capacitive arc radius with increasing the enhancer concentration. The value of R_ct for the blank, epoxy and enhanced epoxy was observed to be 28.86 ± 0.29 Ωcm², 44.88 ± 1.81 Ωcm² and 129.55 ± 3.35 Ωcm², respectively. As the epoxy was enhanced further, ${\epsilon }_{\mathrm{EIS}}$ increased from 35.70% to 77.72% while C_dl increased from 0.006 to 2.185 µF cm⁻².