CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

Chapter 6
for the duplex coating, and greater resistance offered to the charge accumulation on the coated
surface. The circuit parameters for the uncoated, and duplex Ti-TiO 2 coated specimen evaluated
using circuit models as shown in Fig. 3.10a-b are given in Table. 6.5.
Conc.
Fig. 6.15d: Log f vs. Log |Z| for uncoated and Ti-TiO 2 coated 304L SS in 8 M HNO 3 .
Substrate
condition
R s
cm 2 CPE 2
R ct2
cm 2 CPE 1
R ct1
cm 2
C dl2
-1 cm -2 S n
n
(0-1)
C dl1
-1 cm -2 S n
n
(0-1)
1 M Uncoated 2 6.5×10 -5 0.86 9.35×10 2 - - -
1 M Ti-TiO 2 coated 11 1.7×10 -7 0.91 1.24×10 6 1.3×10 -8 0.98 1.1×10 3
8 M Uncoated 1 5.8×10 -4 0.65 1.1×10 2 - - -
8 M Ti-TiO 2 coated 12 2.6×10 -5 0.78 1.8×10 4 1.8×10 -6 0.88 2.8×10 2
Table. 6.5: EIS fitted values for uncoated and duplex Ti-TiO 2 coated 304L SS in 1 M and 8 M
HNO 3 .
Form the circuit parameters, it is obvious that coating resistance or pore resistance (R ct1 )
greatly improves in both the test solution with duplex coating which has not been observed either
for Ti or TiO 2 single layer coating. Apart from this, the coating capacitance (C dl1 ) also showed