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Development of Advanced Electrochemical Emission Spectroscopy for Monitoring Development of Advanced Electrochemical
Emission Spectroscopy for Monitoring
Corrosion in Simulated DOE Liquid Waste
Digby D. Macdonald (PI), Jun Liu (Ph. D., Graduated),
Brian Marx (Grad. Assist.), Balaji Soundararajan (Grad.
Assist.), Morgan Smith (Grad. Assist.), and Sejin Ahn
(Grad. Assist. visiting from Korea).
Center for Electrochemical Science and Technology
Pennsylvania State University
University Park, PA 16802.
May 6-8 2003
Pacific Northwest National Laboratory
Richland, Washington. OBJECTIVES
Develop a fundamental understanding of the corrosion
and stress corrosion cracking of carbon steels in
prototypical DOE liquid waste environments.
Develop methods for deterministically predicting the
accumulation of general and localized corrosion
damage, including pitting attack and stress corrosion
cracking, to liquid waste storage tanks.
Optimize Electrochemical Emission Spectroscopy as a
means of monitoring corrosion in DOE liquid waste
storage tanks. Fundamental Understanding of
Corrosion Processes
Understanding general corrosion in terms of
the Point Defect Model, as revealed by
Electrochemical Impedance Spectroscopy and
Spectroscopic Ellipsometry.
Characterizing the mechanism of passivity
breakdown of nickel (a model system) as
revealed by EIS and Mott-Schottky analysis.
Detecting and characterizing individual micro
fracture events in AISI 4340 steel at the crack
tip.























Fe Metal
Fe
3
O
4
(FeO Fe
2
O
3
) Barrier Layer
Solution





















(1)
'
1
e
V
Fe
Fe
Fe
i
k
+
+
+
(3)
'
)
(
3
e
Fe
Fe
k
i
+
+ +















(2)
'
2
..
2
e
V
Fe
Fe
O
Fe
k
+
+
(4)
+
+
+
H
O
O
H
V
O
k
O
2
4
2
..















(5)
'
)
(
2
2
2
5
e
O
H
Fe
H
FeO
k
+
+
+
+ +

















+ i
Fe




..
O
V




















L
x
=




0
=
x




Figure 1.
Schematic of physicochemical processes that occur within a barrier
oxide (Fe
3
O
4
) layer on passive iron according to the Point Defect Model.
Species include iron atoms; interstitial iron cations; iron vacancies in the
metal phase; iron cations in a normal cation positions; iron cation in the
solution phase; oxygen vacancies; and oxygen ions in anion sites in the film. Formation Potential / V vs. SCE
0.0
0.2
0.4
0.6
0.8
T
h
i
ckness /
nm
1.0
1.5
2.0
2.5
3.0
3.5
4.0
experimental data, pH 8.4
experimental data, pH 8.4 + EDTA
simulated data, pH 8.4+ EDTA
Formation Potential / V vs. SCE
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
St
ea
dy
-S
ta
te
Cu
rrent

Dens
it
y
,
I
SS
/ *10
-6
A
c
m
-2
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
experimental data, ascending voltages, pH 10.0 + EDTA
experimental data, descending voltages, pH 10.0 + EDTA
simulated data, pH 10.0 + EDTA
Figure 2.
The steady-state film
thickness (a) and current
density (b) for the passive film
on iron. Simulated data were
calculated using fundamental
parameters in the Point Defect
Model. Z' (ohms cm
2
)
0
5000
10000
15000
20000
25000
30000
35000
40000
Z
"
(o
hm
s c
m
2
)
-30000
-25000
-20000
-15000
-10000
-5000
0
voltage sweep "up"
voltage sweep "down"
Figure 5.
Nyquist plot for EIS data of the passive film formed on iron in borate
buffer solution with 0.01 M EDTA (pH 8.15) at an applied film formation voltage of
0.2 V vs. SCE. Frequency range is from 10
4
Hz to 10
-2
Hz. Perturbation voltage
amplitude is 10 mV. Passive film formation voltage has been applied at 0.1, 0.2, 0.3,
0.4, 0.5, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1 V vs. SCE continuously with a 24-hour polarization
period for each voltage. Up means changing the formation voltage in the
negative-to-positive direction; down in the positive-to-negative direction. Up
and down voltage measurements have a time interval of 8 days in this case. (a)
Z' (ohms cm
2
)
0
20000
40000
60000
80000
100000
Z
"
(o
hm
s cm
2
)
-80000
-60000
-40000
-20000
0
0.1 V vs. SCE
0.2 V vs. SCE
0.3 V vs. SCE
(b)
Z' (ohms cm
2
)
0
20000
40000
60000
80000
100000 120000 140000 160000
Z" (o
hms
c
m
2
)
-120000
-100000
-80000
-60000
-40000
-20000
0
0.4 V vs. SCE
0.5 V vs. SCE
0.6 V vs. SCE
Figure 6.
Nyquist plot for EIS data
of the passive film formed on iron in
borate buffer solution with 0.01 M
EDTA (pH 10.05) as a function of
formation voltage at a formation
time of 24 hours. Spectra were
measured using an excitation voltage
of 10 mV and an applied frequency
ranging from 10
4
Hz to 10
-2
Hz. (a)
Z' (ohms cm
2
)
0
20000
40000
60000
80000
100000
120000
140000
Z"
(
ohms cm
2
)
-100000
-80000
-60000
-40000
-20000
0
pH = 8.15
pH = 8.94
pH = 10.05
(b)
Frequency (Hz)
10
-2
10
-1
10
0
10
1
10
2
10
3
10
4
Im
pe
danc
e M
odu
lu
s (
ohm
s
cm
2
)
10
0
10
1
10
2
10
3
10
4
10
5
10
6
pH = 8.15
pH = 8.94
pH = 10.05
(c)
Frequency (Hz)
10
-2
10
-1
10
0
10
1
10
2
10
3
10
4
Ph
ase Ang
l
e
(
degr
ees)
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
pH = 8.15
pH = 8.94
pH = 10.05
Figure 7.
Electrochemical impedance
spectra for the passive film formed on
iron in borate buffer / EDTA solution
(formation voltage = 0.6 V vs. SCE) as
a function of solution pH (pH = 8.15,
8.94, 10.05) at a formation time of 24
hours. Spectra were measured using an
excitation voltage of 10 mV and an
applied frequency ranging from 10
4
Hz
to 10
-2
Hz. (a)
Z' (ohms cm
2
)
0
2000
4000
6000
8000
10000
12000
14000
Z" (
o
hm
s
cm
2
)
-10000
-8000
-6000
-4000
-2000
0
pH = 11.27
pH = 12.20
pH = 12.87
(b)
Frequency (Hz)
10
-2
10
-1
10
0
10
1
10
2
10
3
10
4
Im
pedan
ce M
odul
us
(o
hms
cm
2
)
10
-1
10
0
10
1
10
2
10
3
10
4
10
5
pH = 11.27
pH = 12.20
pH = 12.87
(c)
Frequency (Hz)
10
-2
10
-1
10
0
10
1
10
2
10
3
10
4
Ph
ase Angl
e (deg
rees)
-70
-60
-50
-40
-30
-20
-10
0
pH = 11.27
pH = 12.20
pH = 12.87
Figure 8.
Electrochemical impedance
spectra for the passive film formed on
iron in borate buffer / EDTA solution
(formation voltage = 0.6 V vs. SCE) as
a function of solution pH (pH = 11.27,
12.20, 12.87) at a formation time of 24
hours. Spectra were measured using an
excitation voltage of 10 mV and an
applied frequency ranging from 10
4
Hz
to 10
-2
Hz. (a)
Z' (ohms cm
2
)
0
5000 10000 15000 20000 25000 30000 35000 40000 45000 50000
Z"
(
o
hm
s cm
2
)
-35000
-30000
-25000
-20000
-15000
-10000
-5000
0
experimental data
simulated data
(b)
Frequency (Hz)
10
-2
10
-1
10
0
10
1
10
2
10
3
10
4
Im
pedanc
e
M
odul
us
(ohm
s
c
m
2
)
10
0
10
1
10
2
10
3
10
4
10
5
experimental data
simulated data
(c)
Frequency (Hz)
10
-2
10
-1
10
0
10
1
10
2
10
3
10
4
P
has
e A
ngl
e
(deg
rees
)
-100
-80
-60
-40
-20
0
experimental data
simulated data
Figure 9.
Nyquist plot (a) and Bode
plots (b, c) of impedance data for the
passive film formed on iron in borate
buffer solution with 0.01 M EDTA
(pH 8.15) at an applied film
formation voltage of 0.2 V vs. SCE.
Closed circles represent experimental
data and open squares represent
simulated data using nonlinear fitted
parameters. Model Parameter Values for Passive Iron
in Alkaline Media
Transfer coefficients/ standard rate constants 1
= 0.01 k
100
= 3.8e-12 mol.cm
-2
.s
-1 2
= 0.24 k
200
= 1.1e-15 mol.cm
-2
.s
-1 3
= 0.39
k
300
= 2.4e-6 s
-1 5
= 0.30 k
500
= 3.3e-8 mol
0.4
.cm
-0.2
.s
-1
Potential distribution parameters = 0.728 = -0.0047 = 1.10e6
V/cm (Electric field strength)
´ = 30
(Dielectric constant) f/s0
= -0.29
(Constant) Figure 1.
Picture of the spectroscopic ellipsometer and associated systems. The
PC used to collect the ellipsometric and impedance data (a). Two arms of
ellipsometer-use