Corrosion inhibition behavior of urotrpine for steel in hydrochloric acid

The corrosion inhibition and adsorption behavior of urotropine (UP) for steel in a 1 mol·L^-1 hydrochloric acid solution were studied by electrochemical impedance spectroscopy (EIS) and open circuit potential measurements (OCPM). The results of EIS showed that with increasing UP concentration, adsorption film formed gradually on the surface of the electrode and the charge transmission resistance increased. When the concentration of UP is 0.01 mol·L^-1, the maximum of inhibition efficiency was observed. When the concentration of UP was greater than 0.01 mol·L^-1, UP desorbed from the steel surface and made inhibition efficiency decreased. The results of OCPM indicated that the difference of corrosion potential before and after the addition of UP was linear with the reciprocal of temperature. The adsorption heat was -35 kJ·mol^-1, the mode of adsorption was physical adsorption, and UP was an anodic inhibitor.