Corrosion inhibition performance of synergistic inhibitors on Q235 steel in methanol/formic acid medium

Abstract

The corrosion inhibition behaviors of dodecylpyridinium chloride (DPC), hexadecylpyridinium chloride monohydrate (HDPC), and the rosin amino acid surfactants dehydroabietic acylamino sodium (6-DAS) and compounds (6-DAS/DPC and 6-DAS/HDPC) were investigated by weight loss measurements and electrochemical testing. Besides, corrosion inhibition performance was further verified by combining a series of surface properties analyses and theoretical calculations. The weight loss results showed that the increase in inhibition efficiency was mainly attributed to its high concentration and revealed that the inhibition efficiency of compound inhibitors was higher than that of single inhibitor 6-DAS (92.23%), which was up to 95.86% and 96.72% of 6-DAS/DPC and 6-DAS/HDPC at 1:8 concentration ratio, respectively. The potential polarization curve potential demonstrated that single inhibitor 6-DAS and compound inhibitors (6-DAS/DPC and 6-DAS/HDPC) were both mixed-type corrosion inhibitors dominated by the anode. Thus, among the three, 6-DAS/HDPC had the best corrosion inhibition performance, and the average inhibition efficiency was 96.90%. Surface studies presented the adsorption of inhibitor molecules adhered on the Fe surface, while the adsorption performance of compound inhibitors appeared to be superior to single inhibitor 6-DAS. Moreover, it was found that there were a few excellent data from molecular dynamics simulation about the adsorption energies of inhibitors that could also explain the corrosion inhibitor performance, the results of which had good agreement with the experimental data, which provided strong evidence for the close relationship between the molecular structure of inhibitor and its inhibition efficiency.