| Summary: | Inhibition effect of cationic surfactant of tetradecylpyridinium bromide (TDPB) on the corrosion of cold rolled steel (CRS) in phosphoric acid produced by dihydrate wet method process (7.0 M H3PO4) was investigated by weight loss and potentiodynamic polarization methods and electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Quantum chemical calculation was applied to elucidate the adsorption mode of the inhibitor molecule on steel surface. The results show that TDPB acts as a good inhibitor, and its maximum inhibition efficiency is higher than 90% even at low concentration. The adsorption of TDPB obeys the Langmuir adsorption isotherm equation. Polarization curves indicate that TDPB behaves as a mixed-type inhibitor in H3PO4. EIS spectra exhibit one capacitive loop which indicates that the corrosion reaction is controlled by charge transfer process. The inhibition action of TDPB could also be evidenced by surface SEM images. Density functional theory (DFT) calculations suggest that the pyridine ring is the active adsorption center. Depending on the results, the inhibitive mechanism is proposed from the viewpoint of adsorption theory.
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