Abstract

Corrosion inhibition of mild steel in 1.5M HCl by the Terminalia catappa leaves (TCL) extract was undertaken using the gravimetric measurement at 30oC. In order to obtain the maximum inhibition efficiency, optimization of the process variables affecting corrosion of mild steel was carried out using the Box – Behnken Design plan and desirability function of Response surface Methodology (RSM). Three parameters were varied via; inhibitor’s concentration (TCL), immersion time, and temperature and there effects in corrosion inhibition were established. The optimum conditions predicted from the quadratic model were inhibitor’s concentratrion (0.39 g/l), exposure time (8.68 hours), and temperature (36.06 oC) with the inhibitor’s efficiency of 91.95 %. The data fitted well to the quadratic model which was validated. Adsorption of the extract’s component on the mild steel was responsible for the inhibitive effect of the TCL extract on mild steel surface. Statistically, the results showed that 97.92% of the total variation in the inhibition efficiency of TCL can be connected to the variables studied experimentally.

Key words: Mild steel, acid, Terminalia catappa, corrosion, response surface methodology (RSM).