The effect of N and S ratios in N, S co-doped carbon dot inhibitor on metal protection in 1 M HCl solution

Abstract Background The paper article wants to develop a new type of corrosion inhibitor to replace the traditional corrosion inhibitor and reduce environmental pollution. Methods A kind of high-performance N, S co-doped carbon dot (N, S-CDs) inhibitor was synthesized by ammonium citrate and methionine with different ratios (100:0, 95:5, 90:10, 85:15). A series of detection equipment were selected to evaluate the structure and corrosion inhibition behavior of as-obtained inhibitors. The result showed that the as-obtained inhibitors could effectively enhance the impedance of steel in acid environment. With the increase of addition amount, the enhancement degree was increased. In the meantime, the icorr of steel was decreased 1∼2 orders of magnitude in acid solution after adding 200 mg/L inhibitor. Among them, the corrosion inhibition efficiency was the highest and the corrosion rate was the lowest when the ratio of ammonium citrate and methionine was 90:10. The adsorption isotherm revealed that the as-obtained inhibitors could tightly cover on the steel surface by physicochemical interaction. Significant findings This work puts forward the corrosion protection mechanism of N, S-CDs on metal, which can provide technical guidance and basic theories for new corrosion inhibitors in metal corrosion protection.