CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

Chapter 3
where T and n are frequency independent parameters, is the angular frequency, and j
is the imaginary number equal to -./.
(c) Solution resistance (R S ).
The schematic of an electrical equivalent circuit consisting of above circuit elements is
shown in Fig. 3.9 [21]. However, the circuit diagram varies depending upon the nature of working
electrode, and the physico-chemical process occurring at the electrode-electrolyte interface. The
total impedance of the system can be calculated as a combination of the aforementioned circuit
elements.
Fig. 3.9: Schematic of electrode-electrolyte interface in electrochemical impedance spectroscopy
[21].
In the present investigation, electrochemical impedance spectroscopy was used for
investigating the passive film stability of unimplanted and nitrogen ion implanted 304L SS in 1 M
nitric acid. Similarly, EIS study was carried out for uncoated, titanium (Ti), titanium dioxide
(TiO 2 ), and duplex Ti-TiO 2 coated 304L SS for comparing the passive film stability of uncoated,
and coated 304L SS specimens in 1 M and 8 M nitric acid. For unimplanted and nitrogen ion
implanted specimens electrical equivalent circuit as shown in Fig. 3.9 was used to evaluate the
effect of nitrogen on polarization resistance, double layer capacitance, and on the passive film
stability with increase in dose of nitrogen implantation. Similarly, two different electrical