Sustainable Valorization of Palm Fatty Acid Distillate into Amide-based Corrosion Inhibitors for Carbon Steel Protection in CO2-Saline Environments

A PFAD-based amide corrosion inhibitor was synthesized from palm fatty acid distillate (PFAD), an abundant palm oil refining byproduct in Thailand, and diethylenetriamine (DETA) to enhance PFAD value and reduce inhibitor production costs. The synthesized amide was confirmed by 1H NMR, 13C NMR, and FTIR analyses. Its inhibition performance for X65 carbon steel in CO2-saturated 1 wt % NaCl solution was evaluated using LPR, PDP, and EIS at different concentrations. PDP and LPR results showed pronounced decreases in corrosion current density and corrosion rate, with the highest efficiencies of 67.09% and 71.85%, respectively, at 300 ppm, while EIS after 24 h showed a maximum efficiency of 81.97% at 500 ppm. The inhibition performance was attributed to the formation of an adsorbed protective film, demonstrating the potential of PFAD-derived amides as cost-effective and sustainable corrosion inhibitors for oil and gas pipelines.