Adsorption behaviour and corrosion inhibition effect of N. imperialis p. beauv (Lecythidaceae) seed extract on mild steel in 1.0 M HCl

Abstract

The effect of Napoleonaea imperialis seed extract on the corrosion of mild steel in 1.0 M solution of HCl was studied using weight loss measurements at 313 and 333 K. The results obtained from the experiment showed that the seed extract of N.imperialis functioned as an excellent inhibitor against the corrosion of mild steel in 1.0 M solution of HCl. Inhibition efficiency increased with increase in extract concentration and temperature but decreased with immersion time. ?_? values were less than that obtained for the blank, 67.56 kJ/mol and the values of Δ?⁰ were negative and greater than -20 kJ/mol, signifying that the adsorption of N. imperialis on the mild steel surface was chemisorptive and spontaneous respectively. Weight loss data gave best fit with the Langmuir adsorption isotherm model. Chemical adsorption mechanism is proposed for the adsorption behaviour of N. imperialis seeds extract. The corrosion inhibition aligned with the first order kinetics equations.

Keywords: Adsorption isotherm, Corrosion rate, Inhibition efficiency, Mild steel, N. imperialis, Temperature