According to the

Nyquist diagram, in the absence of inhibitor, the steel shows the presence of a depressed capacitive semicircle with a diameter less than 1000 [ohm]-[cm.sup.2].

Caption: Figure 5: EIS

Nyquist diagram evolution for steel rebars of cement mortar (0.3 wt.% chloride) during immersion for 105 days in 0.1 M NaOH solution: (a) without epoxy coating, (b) with epoxy coating, (c) with nano-[Fe.sub.2][O.sub.3] modified epoxy coating, and (d) with nano-Si[O.sub.2] modified epoxy coating.

Nyquist Diagram. Open-loop transfer function can be written as

An analogous diagram is also employed to plot transfer functions and is called

Nyquist diagram. The parameters of the transfer function can be determined and the stability of a system can be analyzed thereby with it.

8(b), after 120 days of immersion, the second loop appeared in the

Nyquist diagram of NR coating which means the corrosion reactions.

As the analyzed oscillator is a negative resistance topology, the more interesting

Nyquist diagram is the [Z.sub.T] one (see Fig.

In a

Nyquist diagram, Im(Z) is plotted against Re(Z), and frequency is contained implicitly.

The comparation with the identified model (Fig.3.), through the

Nyquist diagram has not led to the selection of any variant and that to be proceeded to extend the grade and we have obtained a series of values for the coefficients.

A semicircle

Nyquist diagram indicates that the sensor could be described by the Randles equivalent circuit as shown in Figure 10(a).

The

Nyquist diagram of an immersed sample at five points of time namely, at the beginning of the experiment, after 26 days, 69 days, 98 days, and after 117 days is presented in Fig.

It is said that analysis of the Bode diagram is simpler than the

Nyquist diagrams. Bode format minimizes the dispersion of the experimental data and shows a clearer description of the frequency-dependent behavior of the electrochemical system, which only is implicit in the

Nyquist diagrams.

Figure 3 shows the

Nyquist diagrams of the Al-6Si-0.5Mg-xCu alloys in 0.1 M NaCl solution.