In-depth insight into the synergistic inhibition mechanism of Centella asiatica extract and KI on the corrosion of carbon steel in acidic medium

Carbon steel (CS) experiences significant corrosion when exposed to acidic medium. To address this issue, an eco-friendly corrosion inhibitor derived from Centella asiatica extract (CAE) has been developed. The representative components for CAE were revealed using FTIR and LC-MS analyses. Subsequently, the corrosion inhibition performance of CAE and CAE + KI on CS in test media was investigated. Experiments and theoretical calculations were used to explore inhibitive property and adsorption behavior of CAE and CAE + KI. The electrochemical measurements show that the inhibition efficiency of 200 mg/L CAE + 200 mg/L KI reaches 96.9 % at 25 °C. Surface analyses confirm that the addition of CAE + KI could effectively alleviate CS corrosion. Additionally, theoretical calculations have proved that the adsorption of the representative components of CAE on CS surface is mainly achieved through O, C atoms. Overall, the good inhibition efficiency, wide source of raw materials and straightforward extraction method render CAE promising as an industrial corrosion inhibitor. • CAE and KI were tested as combined corrosion inhibitors for carbon steel. • Electrochemical tests indicate that CAE and KI exhibit synergism inhibition effect. • The adsorption of CAE and KI on carbon steel surface is strengthened after mixing. • The CAE + KI film can prevent the diffusion of corrosive species to steel surface. • The synergetic mechanism of CAE and KI was probed by theoretical calculations.