The synergistic effect of sodium phytate and benzotriazole as corrosion inhibitors of 20SiMn steel in 3.5 wt-% NaCl solution

ABSTRACT The synergistic inhibition effect of sodium phytate (PA) and benzotriazole (BTA) on 20SiMn steel in 3.5 wt-% NaCl solutions was studied using electrochemical methods, SEM, FTIR, XPS and quantum chemical calculations based on density functional theory (DFT). Results indicate that a protective bi-layer film is formed with the presence of the mixture of PA and BTA: the inner layer consists of iron oxides, while the outer one is an adsorption layer of BTA and PA. Based on the analysis of XPS and DFT, the function of BTA belongs to chemisorption, while that of PA obeys Langmuir adsorption isotherm and could be mainly assigned to physisorption. The inhibition efficiency of the mixture inhibitor is 99.12%, with a synergism parameter of 3.62, which could be ascribed to a cross-linking structure containing more BTA promoted by PA through hydrogen bonds.