N-(4-methoxybenzylidene)-R-1,3,4-thiadiazole-2-amine Schiff base as high-performance corrosion inhibitor on copper sheet in 3.5 Wt.% NaCl solution

Purpose This study aims to synthesize a series of thiadiazole Schiff base compounds with excellent anticorrosion behavior on copper in 3.5 Wt.% NaCl solution. Design/methodology/approach 4 N-(4-methoxybenzylidene)-R-1,3,4-thiadiazole-2-amine Schiff base compounds were successfully synthesized, where R represented hydrogen (-H, A1), thiol (-SH, A2), methyl (-CH3, A3) and bromo (-Br, A4), respectively. The molecular structure was confirmed by 1H NMR, 13C NMR and FT-IR measurements. The corrosion inhibition effect of the four compounds on copper in 3.5 Wt.% NaCl solution was evaluated by electrochemical method and surface analysis technology. The corrosion inhibition mechanism was analyzed by Langmuir adsorption isotherm, quantum chemical calculation and molecular dynamics simulation. Findings The polarization tests showed that the corrosion potential of the test pieces all shifted to the positive direction, and the A2 Schiff base was of the best corrosion inhibition performance on copper. Quantum chemical calculation verified that the adsorption activity of these four inhibitors was A2>A4>A3>A1. The adsorption kinetics results showed that these four inhibitors existed on the copper surface with a parallel manner, which conformed to Langmuir adsorption isotherm model. Originality/value Four novel corrosion inhibitors were successfully prepared, and they exhibited excellent corrosion resistance on copper in 3.5 Wt.% NaCl solution. The introduction of imine bond (-C = N-), and hetero-atoms such as N, S, O could significantly improve the corrosion inhibition effect. This work provides a theoretical basis for the design of efficient corrosion inhibitors.