2-Amino-5-(4-pyridinyl)-1,3,4-thiadiazole monolayers on copper surface: Observation of the relationship between its corrosion inhibition and adsorption structure

•2-Amino-5-(4-pyridinyl)-1,3,4-thiadiazole (4-APTD) was modified at copper surface.•4-APTD film was proved to protect copper electrode from corrosion in KCl solution.•SERS analysis found adsorption of 4-APTD on copper surface was via N3 and N12 atoms. Corrosion inhibition behavior of 2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole (4-APTD) monolayers on copper surface were investigated by electrochemical impedance spectroscopy (EIS), electrochemical polarization measurement and surface-enhanced Raman scattering (SERS) experiment. The EIS mechanism of the copper surface with 4-APTD monolayers fitted to the mode of R(Q(R(QR))). The electrochemical polarization measurements indicated high inhibition efficiency of about 90.4%. SERS results suggested that 4-APTD molecules anchored at copper surface in a tilted orientation directly via N3 and N12 atoms. The transition adsorption states of 4-APTD on the copper surface were observed as the potential applied from 0 to −1.6V vs. SCE.