Evaluation of Corynocarpus laevigatus extract as a green corrosion retardant for mild steel in acidic media: A combined gravimetric, gasometric and electrochemical methods
Anthony I. Obike, K.S. Eze, Ibrahim Abdel‐Rahman, Alexander I. Ikeuba, Izuchukwu K. Nwokolo, Christopher U Aghalibe
Abstract
The corrosion inhibition by the methanolic extract of Corynocarpus laevigatus leaves on mild steel within acidic environments was evaluated utilizing gravimetric, gasometric, and electrochemical methodologies. The findings indicate that the extracts serve as an effective corrosion inhibitor in both H 2 SO 4 and HCl aqueous solutions. The extract exhibited optimum inhibition efficiencies of 88.64 %, 71.12 %, and 77.60 % in H 2 SO 4 , and 88.89 %, 67.96 %, and 85.55 % in HCl, respectively. The inhibition efficiency increased with higher extract concentrations but decreased with increasing temperature and exposure time in both media. Also, the rate of hydrogen evolution increased with rising temperature in both media. Adsorption studies revealed that the inhibitor's average activation energy ( Ea ) values were 71.23 kJ/mol and 137.59 kJ/mol for H 2 SO 4 and HCl media, respectively. The extract followed the Langmuir isotherm model, indicating monolayer adsorption of the phytochemical components onto the mild steel surface. Physical adsorption was dominant in H 2 SO 4 , as evidenced by decreasing activation energy ( Ea ) values with increasing temperature. In contrast, chemical adsorption was observed in HCl. The strong adsorption of phytochemicals present in the extract onto the steel surface was identified as the primary mechanism for corrosion inhibition. This study provides valuable insights into the dual adsorption mechanisms of Corynocarpus laevigatus in different acidic media which underscores its potential as a sustainable and effective corrosion inhibitor in acidic environments. • Methanolic extract derived from the leaves of this particular plant serves as an effective corrosion inhibitor in both H 2 SO 4 and HCl aqueous solutions. •The efficiency of corrosion inhibition was found to increase with the increase of extract concentrations, while it decreased with the rise in both time and temperature across both media. •The corrosion inhibition efficiency is ascribed to the pronounced adsorption of the phytochemicals present within this extract onto the metal surface. •The proposed mechanism of adsorption for the plant extract is characterized as physical adsorption in H 2 SO 4 media and chemical adsorption in HCl media.