Corrosion inhibition of mild steel in HCl solution using an eco-friendly and cost-effective okra water extract

Abstract This study aimed to develop an environmentally friendly corrosion inhibitor derived from okra extract to mitigate corrosion damage of mild steel in 1 M hydrochloric acid (HCl) solution. The optimal concentration of the extract was determined through weight loss and electrochemical measurements. Scanning electron microscopy was applied to characterize the surface morphology of specimens before and after corrosion behavior. The results indicated that mild steel underwent severe corrosion in 1 M HCl, which was significantly inhibited after the addition of okra extract. The inhibition efficiency increased with higher concentrations of the extract, exceeding 90 % at 8,000 mg/L. The adsorption behavior of inhibitor followed the Langmuir isotherm and was determined to be physical type. Fourier transform infrared spectroscopy (FT-IR) was conducted and found O–H, C–H, C=O, C=C and C–O bonds are abundant in okra extract, which has significant meaning on the adsorption of okra extract molecules onto the substrate. Furthermore, theoretical quantum chemical calculations were employed to elucidate the corrosion inhibition mechanism, revealing that glucose and rhamnose components in the extract contribute effectively to the corrosion protection of mild steel in HCl solution.