Evaluation of alkaloids extract of Retama monosperma (L.) Boiss. stems as a green corrosion inhibitor for carbon steel in pickling acidic medium by means of gravimetric, AC impedance and surface studies

The present work is devoted to the study of alkaloids extract from Retama monosperma stems (AERST) as green corrosion inhibitor to afford the protection of carbon steel in 1 M HCl medium at 30°C. Weight loss and AC impedance techniques were coupled with Scanning Electron Microscopy (AERST) and X-Ray Photoelectron Spectroscopy (XPS) analyses to characterize the inhibitive properties of AERST and to determine the chemical composition of the inhibitive film formed on the steel surface. AERST inhibited the corrosion of carbon steel in 1 M HCl, and its inhibition efficiency increased with the inhibitor concentration. However, a maximum inhibition efficiency of 83% was reached with 400 mg/L of AERST at 30°C. Adsorption of AERST on the steel surface in 1 M HCl solution followed Langmuir’s isotherm. The XPS studies showed that the inhibitive layer is composed of an iron oxide/hydroxide mixture where AERST molecules are incorporated.