## Given the importance of this factor we have plotted

Fig. 2 shows the Nyquist plots for the corrosion of iron in 1 M HCl in the absence and presence of TCID LC3C12. The impedance spectra obtained consist of one capacitive loop. The main parameters deduced from the analysis of Nyquist diagram are:-the resistance of charge transfer Rct,-the capacity of double layer Cdl.

Fig. 2. Nyquist diagrams of iron in 1 M HCl without and with addition of LC3C12 at different concentrations. () 0%, () 5 × 10−6 M, () 5 × 10−5 M, () 10−4 M, () 2 × 10−4 M.Figure optionsDownload full-size imageDownload as PowerPoint slide

The values of the polarization resistance were calculated by subtracting the high frequency intersection from the low frequency intersection [1]. Double layer capacitance values were obtained at maximum frequency at which the imaginary part of the Nyquist plots is nervous system maximum and calculated using the following equation:equation(7)Cdl=1Rct2Ï€fcwhere fc is the maximum frequency.