Inhibition Performance of Alternanthera Philoxeroide Extract on Cold Rolled Steel in HCl Solution

Alternanthera philoxeroide extract (APE) was obtained using ethanol aqueous solution as extractant, and the functional groups and UV absorption curves of APE were characterized by infrared spectroscopy (FTIR) and ultraviolet spectroscopy (UV). The corrosion inhibition performance of APE on coldrolled steel in 0.50 mol/L HCl solution was studied using weightlessness method, electrochemical method, scanning electron microscope (SEM) observation, and contact angle test. The results showed that APE had a significant corrosion inhibition effect on cold rolled steel in HCl solution, and the corrosion inhibition rate of 100 mg/LAPE reached 97.1% at 50 ℃. The corrosion inhibition rate increased firstly and then stabilized with the increase of the corrosion inhibitor dose, and slightly increased as the temperature increased. APE was a mixed corrosion inhibitor, and its electrochemical mechanism on the surface of cold-rolled steel was “geometric coverage effect”; the charge transfer resistance increased significantly after the addition of APE, but the capacitance value of the electric double layer at the interface decreased. The adsorption of APE on the surface of steel conformed to the apparent Langmuir adsorption isotherm. There were both chemical adsorption and physical adsorption. SEM observation and contact angle test results showed that APE significantly slowed down the corrosion of cold-rolled steel and enhanced the hydrophobicity on the surface of the cold-rolled steel.