Mathematical modelling of corrosion inhibition of mild steel in acidic medium using response surface central composite design

Abstract

Corrosion is a threat to engineering materials and one vital way of preventing it is through the use of inhibitors especially the green inhibitors which are eco – friendly. The aim of this work is to develop a mathematical model for predicting corrosion rate of mild steel in acidic medium using Musa Sapientum peels extracts as inhibitors. It also involves minimizing corrosion rate through investigations of influence of inhibitor concentrations and immersed time with the aid of central composite design (CCD) of response surface. The method of Salami and Umar was used in the preparation of the inhibitor extract and mild steel coupons used in this study while weight loss method was adopted for the measurement of corrosion rate. The least corrosion rate obtained was 5.58 mm/yr at the inhibition concentration and immersed time of 0.924 g/L and 60 hrs respectively while the highest corrosion rate was 30.9 mm/yr at the inhibition concentration and immersed time of 0.2 g/L and 96 hrs respectively. The optimum inhibition concentration, immersed time and corrosion rate were 0.076 g/L, 9.083 hrs and 17.005 mm/yr respectively however the minimum corrosion rate of 5.58 mm/yr is preferred to optimum corrosion rate of 17.005 mm/yr as the 5.58 was obtained by ostensibly better conditions that is 5.58 mm/yr was obtained through a real experiment process and not under simulation conditions and due to economics. The developed second order regression model predicted the experimental data up to 93.30 percent confidence level hence it can be used to navigate the design space and for theoretical prediction of corrosion rate.