Pueraria lobata leaf extract as green corrosion inhibitor for low carbon steel in 1.0 M HCl solution

Plant corrosion inhibitors in acid-pickling environment have the advantages of wide source, low cost and environmental protection. Pueraria lobata leaf extract (PLLE) was prepared by the combination of soaking method and ultrasonic extraction method. HPLC characterization found that PLLE contains some active ingredients, such as Puerarin, Biochanin, Daidzin and Daidzein. The corrosion inhibition of PLLE on 10# steel in 1.0 M HCl solution was studied by weight loss analysis, potentiodynamic polarization measurement, electrochemical impedance spectroscopy, scanning Kelvin probe test (SKP) and scanning electron microscopy. The results show that PLLE can effectively inhibit the corrosion of 10# steel in HCl, when the temperature is 25 °C, adding 0.5 g/L PLLE to 1.0 M HCl solution, the corrosion inhibition efficiency of 10# steel can reach up to 94.37%. The SKP results show that after adding PLLE to HCl, the surface potential difference and electrochemical non-uniformity of 10# steel are reduced, and the local corrosion tendency is significantly reduced. Polarization curves and electrochemical impedance spectroscopy indicate that PLLE is a mixed corrosion inhibitor. The adsorption process is mainly chemisorption and obeyed the Langmuir model.