Corydalis yanhusuo extract as a green inhibitor for J55 steel in 3.5%NaCl solution saturated with CO2

ABSTRACT In this study, Corydalis yanhusuo extract acts as a green inhibitor for J55 steel in 3.5% NaCl solution saturated with CO2. Rapid resolution liquid chromatography shows the concentrations of Palmatine to be 0.6358？g/L, Tetrahydropalmatine 0.7715？g/L, and Corydaline 0.3755？g/L. Potentiodynamic polarization results suggest that Corydalis yanhusuo extract is a mixed-type inhibitor. The inhibition efficiency of Corydalis yanhusuo extract increases with the increase of concentration and reaches 92.36% at 5%v/v but decrease with the increased temperature. The inhibition efficiency is 69% at 80°C. The protective film formed on the metal surface was confirmed by Fourier transforms infrared spectroscopy, UV–visible, scanning electrochemical microscope and scanning electron microscope methods. The quantum chemical calculations predicate that Palmatine acts as the major component for inhibition performance. GRAPHICAL ABSTRAC