A novel amide corrosion inhibitor derived from waste cooking oil for mild steel in hydrochloric acid

This study investigates the transformation of waste cooking oils into amides to serve as corrosion inhibitors for carbon steel in hydrochloric acid environments. Fourier-transformed infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (¹HNMR) methods were then used to analyze the presence of amides inhibitors. The application of inhibitor to carbon steel prior to immersion in hydrochloric acid was effective in delaying the corrosion rate and increasing resistance towards corrosion by forming a protective barrier on the surface. The effects of temperature and inhibitory ratio on the efficacy of corrosion inhibition under various conditions were also determined. The maximum effectiveness of 88.5% was attained at 298 K with an inhibitor ratio of 2000 ppm. Kinetic analysis at different temperatures was also carried out to determine the response mechanisms of inhibitors. According to the inhibitor thermal adsorption isotherm, the steel surface is complexed based on the Langmuir adsorption isotherm. Inhibition and corrosion investigations were also performed by using electrochemical impedance spectroscopy (EIS). Scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy study established the existence of a protective adsorbed film of inhibitor molecules over the metal surface. This study contributes to the advancement of science and engineering pertaining to improved corrosion resistance under acidic conditions and the mitigation of used cooking oils.