Anticorrosive behaviors of 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) on a cobalt film electrode surface were comparatively studied by means of electrochemical techniques such as cyclic voltammetry, polarization curves, and electrochemical impedance spectroscopy. The anticorrosion ability of AMT on a Co electrode in a neutral solution was confirmed at the macroscopic level. The adsorption geometry of AMT and the inhibition mechanism were further investigated by in situ electrochemical surface-enhanced infrared reflection absorption spectroscopy and surface-enhanced Raman scattering techniques. Free and adsorbed AMT information by theoretical calculations provided the powerful supports for the assignments of the bands and the establishment of the adsorption configurations. The results implied that the adsorbed AMT molecules were bonded to the Co electrode surface via the S1, S6, and N7 atoms at a small angle, with their ring planes tilted to the local surface at the potential negative of −0.4 V (vs SCE). At the potential positive to −0.2 V (vs SCE) or open circuit potential, AMT probably adsorbed on the Co surface with its molecular plane perpendicular to the surface through both S atoms as a transition state, and AMT molecules may finally function with the Co surface via N3 and N7 atoms as a vertical orientation with respect to the surface at 0 V (vs SCE). These compact barrier layers on the metal surface had great inhibition effects.

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