Abstract: It is investigated that the inhibition of pyridine, quinoline and their derivatives for the corrosion of mild steel in 1 mol/L HCl solution by weight-loss, impedance and polarization techniques. It is found that these compounds can inhibit both cathodic and anodic processes of mild steel. The corrosion potential shifts to less noble direction. The inhibition efficiency obtained by weight-loss is in good agreement with that obtained by impedance method. According to the relationship of the degree of coverage of pyridine or quinoline to its bulk concentration and system temperature, the adsorption of both inhibitors on mild steel follows Flory-Huggins isotherm. Thus, the thermodynamic parameters of the adsorption of pyridine and quinoline are evaluated from the adsorption isotherm. A possible adsorption modle of pyridine, quinoline and their derivatives on the surface of mild steel is also proposed.

Key words: Inhibitor, Inhibition, Adsorption