β-Sitosterol isolated from rice hulls as an efficient corrosion inhibitor for mild steel in acidic environments

Abstract

β-Sitosterol has an inhibiting effect on the corrosion of mild steel. We investigated this effect in a H₂SO₄ solution using β-sitosterol-3-O-β-D-glucoside (β-sitosterol) isolated from rice hulls. Proton nuclear magnetic resonance, UV-visible spectroscopy, FT-IR spectroscopy, weight loss measurements, electrochemical studies, and atomic absorption spectroscopy were used to examine the inhibition of β-sitosterol on mild steel corrosion in a 1 M H₂SO₄ solution. The effect of temperature on the corrosion behavior of mild steel was examined in the range of 303–333 ± 1 K. The inhibition efficiency increased with increasing inhibitor concentration and decreased with increasing temperature. Electrochemical studies indicated that isolated β-sitosterol acted as a good corrosion inhibitor. The surface morphologies of the mild steel specimens were analyzed by scanning electron microscopy. The maximum inhibition efficiency of β-sitosterol (500 ppm) was 95%. The surface morphology was identified using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDS), and atomic force microscopy (AFM).