Corrosion Inhibition of Mild Steel in Aqueous HCl using Bitter Leaf and Fenugreek Seed Oils

Abstract

Bitter leaf and Fenugreek seed oils were extracted from their parent seed plants for use as corrosion inhibitors for mild steel in HCl. Corrosion measurements were taken at a time interval of 72 h. The Fenugreek seed oil gave 90% efficiency with a regression coefficient of 0.99 in terms of its ability to resist HCl corrosion, while the bitter leaf oil extract gave a corrosion inhibition efficiency of 87% with a regression coefficient of 0.84. Based on analyses, the adsorption of the extracts to mild steel obeyed better, the Langmuir adsorption isotherm. From the calculated ∆Gs, the adsorption of Fenugreek and bitter leaf oils on the surface of the mild steel as corrosion inhibitors, were found to be clearly descriptive of physiosorption and chemisorption respectively. Furthermore, the FLE and BLE adsorption behavior on the mild steel can be described as that of mixed-type inhibitor. Based on the phytochemical test conducted, the better performance of the FLE relative to the BLE may be as a result of terpenoids which are present in the FLE.