Inhibitive effect of different solvent fractions of bamboo shoots extract on the corrosion of mild steel in 0.5 mol/L H₂SO₄ solution

The ethanol extract of bamboo shoots was obtained by refluxing bamboo shoots in 95 % ethanol, and then the ethanol extract from bamboo shoots were separated by organic solvents with different polarity, including petroleum ether, dichloromethane, ethyl acetate and n-butanol. The inhibitive effect of different solvent extraction fractions of bamboo shoot extract on the corrosion of mild steel in 0.5 mol/L H₂SO₄ solution was investigated through electrochemical technique, weight loss test, scanning electron microscope and X-ray photoelectron spectroscopy. Electrochemical results showed that all extraction fractions of bamboo shoots extract, as modest cathodic inhibitors, mainly inhibited the cathodic reaction of mild steel in 0.5 mol/L H₂SO₄ solution, and the inhibition efficiency of extraction fraction increased with the increase in its concentration. When the concentration was 0.4 g/L, the corrosion inhibition efficiency of dichloromethane fraction (DCMF), n-butanol fraction (nBF), ethyl acetate fraction (EAF) and the residual fraction (RF) are 93.03%, 89.62%, 85.33% and 64.84%, respectively. However, the results of weight loss experiment showed that when the experimental time increased from 4 h to 24 h, the inhibition efficiency of DCMF and EAF decreased significantly, but that of nBF remained at about 86%, showing a better long-term effect. Surface analysis technology was used to investigate the corrosion inhibition and adsorption behavior of the extraction extraction fractions, and the adsorption of different solvent extraction fractions of bamboo shoot ethanol extract on mild steel surface was in accordance with the equation of Langmuir isotherm.