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.
. 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.