Insight into interfacial adsorption and inhibition mechanism of Aconitum carmichaelii Debx extract as high-efficient corrosion inhibitor for carbon steel in acidic solution

Aconitum carmichaelii Debx, which comes from the buttercup plant, is a common herbal remedy. Its main components have the potential to be employed as corrosion inhibitors. In this work, the corrosion inhibition properties of Aconitum carmichaelii Debx extract on carbon steel in acidic solution were investigated for the first time. Its inhibitive effect was assessed by electrochemical methods and surface characterization. It is confirmed that the inhibitive effect of Aconitum carmichaelii Debx extract exhibited outstanding corrosion inhibition efficiency of 98.1 % at 200 mg/L, which is more than many of the reported plant extracts in the literature. It is also found that the Aconitum carmichaelii Debx extract exhibits a good inhibition stability, with the inhibition efficiency of 98.9 % after 72 h exposure. In addition, theoretical calculations were performed to further investigate the adsorption mechanism of Aconitum carmichaelii Debx extract on carbon steel surface. GFN-xTB (Geometries, Frequencies, Noncovalent interactions eXtended Tight Binding) calculations reveal that the main chemical compositions of Aconitum carmichaelii Debx (1-methyl-1,2,3,4-tetrahydroisoquinoline-6,7-diol (MTD), 1-(4-hydroxybenzyl)1,2,3,4-tetrahydroisoquinoline-6,7-diol (HTD)) could adsorb on the steel surface through the O and N atoms. Therefore, Aconitum carmichaelii Debx extract, with good inhibition efficiency and convenient extraction process, is expected to be a new type of industrial corrosion inhibitor, thus promoting the development of environmentally friendly corrosion inhibitors in plant extract products.