Synergistic inhibition between dodecylamine and potassium iodide on the corrosion of cold rolled steel in 0.1 M phosphoric acid

Abstract The corrosion inhibition of cold rolled steel in 0.1 M aerated phosphoric acid (H₃PO₄) in the presence of dodecylamine (DDA) and potassium iodide (KI) has been investigated by Tafel polarization curve and electrochemical impedence spectroscopy (EIS) at 20 °C. The results obtained from polarization curve show that the inhibition efficiency of DDA with and without KI increases with increase in concentration of DDA but the inhibition efficiency of DDA without KI is not too high. A synergistic effect exists when DDA and KI are combined together to prevent cold rolled steel corrosion in 0.1 M H₃PO₄. All impedance spectra in EIS tests exhibit one capacitive loop which indicates that the corrosion reaction is controlled by charge transfer process. Inhibition efficiencies obtained from Tafel polarization, transfer resistance (R_t) are consistent.