Abstract: The effect of thiourea(TU) on the corrosion behavior of bulk nanocrystallized and coarse grain industrial pure iron in 1 mol•L－1 HCl at room temperature was investigated, by means of electrochemical impedance spectroscopy(EIS).Bulk nanocrystallized industrial pure iron is less prone to get corrosive than its coarse grain counterpart in blank 1 mol•L－1 HCl at room temperature from the EIS fitting results. On the basis of the variation of impedance behaviors of bulk nanocrystallized and coarse grain industrial pure iron in the inhibitor-containing 1 mol•L－1 HCl solutions with the immersion time, an relationship between immersion time and Nyquist plot was established, for very short immersion time,namely,5 min, an inductive loop appeared at different concentrations in the Nyquist plots of coarse industrial pure iron rod, but it did not appear in those of nanocrystallized industrial pure iron. A critical concentration of thiourea with the largest Rct (charge transfer resistance) in the complex impedance plane appeared for both samples.

Key words: Bulk nanocrystallized industrial pure iron, Thiourea, Inhibition, 　Electrochemical impedance spectroscopy (EIS), Hydrochloridic Solution