Corrosion Inhibition Behaviour for Mild Steel by Extracts of Musa sapientum Peels in HCl Solution: Kinetics and Thermodynamics Study

Abstract

The inhibition of the corrosion of mild steel by acid extract of Musa sapientum peels in 1M HCl was investigated using weight loss method. The results showed that the corrosion rate of mild steel in 1M HCl decreases with increase in concentration of the extracts and the values were in the range 0.013021 - 0.002127 ghr -1 cm -2 . The inhibition efficiency increases progressively as the concentration of the extracts increases up to about 4% (v/v), above which, further increase in extract concentration did not cause any significant change in the inhibition efficiency. Effects of temperature on the inhibition efficiency of the extracts showed that inhibition efficiency decreases with increase in temperature. Activation energy (Ea) was found to be 61.60 Kjmol -1 for 1M HCl and increases to 66.72Kjmol -1 in the presence of Musa sapientum extract. The values for enthalpy of activation and entropy were all positive indicating the endothermic nature of the mild steel dissolution process. Calculated Gibbs free energy was in the range -9.43 to -8.99KJ. Kinetics of the reaction in the presence of the extracts revealed that it follows a first order reaction and the half-life increases as the concentration of the extracts increases suggesting that inhibition efficiency increases with increase in the concentration of the extracts. Preliminary investigation of the phytochemical constituents showed that Musa sapientumcontains tannin, flavonoid, terpenoid and some other compounds in trace constituents. Keywords-Steel corrosion, inhibitor, Musa sapientum, kinetics, and thermodynamics