Polarization and impedance measurements were used in this study on inhibitor effects on the anodic behavior of iron electrodes showing that the sharp Tafel slope decreases of the anodic polarization curves resulted from inhibitor desorption for iron electrodes in addic solution containing some types of inhibitors.An electrochemical parameter, desorption potential Edes was proposed as the potential at which the adsorbed inhibitor layer begins to desorb irreversibly. The impedance measurements indicated that at the desorption potential Edes, the double layer capacitances began to increase drastically. The current density re sponses to a potential step showed the inhibitor desorbing rates depended on the differences between the desorption and applied potentials. The larger the potential difference was, the faster the inhibitor desorbed.When the applied potential was lower than Edes, no inhibitor desorption occurred. Polarization and impedance measurements were used in this study on inhibitor effects on the anodic behavior of iron electrodes showing that the sharp Tafel slope decreases of anodic polarization curves caused from inhibitor desorption for iron electrodes in addic solution containing some types of inhibitors. , the desorption potential Edes was proposed as the potential at which the adsorbed inhibitor layer begins to desorb irreversibly. The impedance measurements indicated that at the desorption potential Edes, the double layer capacitances began to increase drastically. The current density re sponses to a potential step showed the inhibitor desorbing rates depended on the differences between the desorption and applied potentials. The larger the potential difference was, the faster the inhibitor desorbed .When the applied potential was lower than Edes, no inhibitor desorption occurred.