Optimization analysis of epoxidation of silkworm pupae oil with citric acid and eco-friendly oil coating on mild steel for corrosion protection

Silkworm pupae oil (SPO) with high amount of unsaturation due to rich in oleic acid and alpha-linolenic acids has been chosen for this investigation. Epoxidized silkworm pupae oil (ESPO) was produced by in situ generated peroxycitric with citric acid (CA) and hydrogen peroxide (H2O2). Literature covering the topic of epoxidation, including the catalytic aspect, is vast. No review articles have been written on the synthesis of epoxides from SPO without the catalyst to the best of our knowledge. Here, CA itself behaves as an oxygen carrier without any catalyst and H2O2 as an oxygen donor, which favors the epoxidation reaction. The epoxidation process was optimized by factors like temperature, time, and CA ratio. Fourier transform infrared (FTIR) analysis confirmed the presence of epoxy groups and the absence of (-C=C-) bonds in ESPO. Optimal conditions for epoxidation were 70 degrees C, 0.75 mol/L CA, and 7 h, resulting in 92.1% double bond conversion (DBC) and 84.7% relative oxirane conversion (RC). The polymerized ESPO coated on mild steel (MS) exhibited enhanced corrosion resistance, with inhibition efficiency rising from 83.86% to 99.42% due to effective pore prevention and ion modification during curing.