Evaluating the synergistic effect of maple leaves extract and iodide ions on corrosion inhibition of Q235 steel in H2SO4 solution

In recent years, many plant extracts have been used as green corrosion inhibitors to replace traditional corrosion inhibitors, but their inhibition performance still needs to be improved. The synergistic corrosion inhibition behavior and mechanism of maple leaves extract (MLE) and potassium iodide (KI) on Q235 steel in 0.5 M H2SO4 solution were firstly investigated in this work. The results demonstrate that both MLE and KI can prevent the corrosion of steel in corrosive media, and that their combined protection effect is superior. The corrosion inhibition efficiency (η) value reaches 93.4 % in corrosive solution with the combination of 200 mg/L MLE and 200 mg/L KI, while the maximum of η is only 81.6 % using MLE alone. In addition, Fe-N bond and Fe-O bond were found on the steel surface through the X-ray photoelectron spectroscopy (XPS) analysis, which confirm the formation of a protective film. The adsorption behavior of an inhibitory film composed of MLE and KI mixtures onto steel surface follows the Langmuir adsorption isotherm model, consisting of physisorption and chemisorption. Finally, molecular dynamics (MD) simulation indicates that inhibitor molecules can adsorb on the Fe substrate in a parallel way with high binding energy values, which supports the experiments well.