Vanillin modified chitosan as a new bio-inspired corrosion inhibitor for carbon steel in oil-well acidizing relevant to petroleum industry

Due to strict environmental regulations, the use of toxic chemicals as corrosion inhibitors for the oil-well acidizing is restricted. Environmentally benign Vanillin-modified chitosan (Van-Cht) is synthesized using a microwave-induced green synthetic protocol and thoroughly characterized by FTIR and NMR spectroscopy. The inhibitor has been evaluated for the first time for carbon steel in 15% HCl. The corrosion inhibition performance was assayed using weight loss and electrochemical methods complemented with the surface analysis of the corroded carbon steel samples without and with the inhibitor immersed in the corrosive medium. Results obtained showed that the Van-Cht acted by adsorption on the surface of carbon steel to inhibit corrosion and exhibited a mixed-type behavior with cathodic predominance. The adsorption of Van-Cht on the carbon steel surface obeyed the Langmuir isotherm. The excellent corrosion inhibition efficiency of > 98% observed at a concentration of 500 mg L−1. Surface analysis using SEM and FTIR-ATR measurements supported the adsorption of Van-Cht inhibitor on the carbon steel surface. The pKa analysis proved that the inhibitor Van-Cht exists mainly in the protonated form at the experimental pH. The density functional theory (DFT) analysis proved that the protonated form of the Van-Cht inhibitor behaves better compared to that of the Van and neutral Van-Cht.