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|Z| (ohm) Phase angle (degrees) 10 6 0 10 5 5 h 23 h 52 h 73 h 168 h 336 h -80 -60 10 4 -40 10 3 -20 10 2 10 -2 10 -1 10 0 10 1 10 2 10 3 Frequency (Hz) 10 4 10 5 Figure 3.39. Bode magnitude and phase angle plots of Neat Epoxy coating upon static exposure to 0.5M NaCl solution for a period of 2 weeks (336 h). The area exposed to the solution was 5.55 cm 2 Figure 3.40a shows the total magnitude of impedance at 0.01 Hz of the coatings relative to the SrCr.Ep standard. Better response was seen from the bentonite pigmented coatings at the end of 680 h with the impedance of 5ZnB.Ep (1.51 x10 6 Ω.cm 2 ) and 5LaB.Ep (1.79 x10 6 Ω.cm 2 ) in the same order of magnitude as SrCr.Ep (2.48 x 10 6 Ω.cm 2 ). Interestingly, Ce and Pr bentonite pigments showed inferior performance compared to the other bentonites. The water uptake by the pigmented coatings is causing the release of the Zn 2+ and La 3+ cations from the pigments and promoting passivity of the interface. Figure 3.40b shows the variation in coating capacitances with time over 680 h relative to the SrCr.Ep control. There is some incongruence in the interpretation as the coating capacitances of the bentonites are too high on the order of 10 -7 to 10 -8 , which cannot be coating capacitances. As a check, the dielectric constant of a coating with thickness, t, is given by ε = Ct/Aε o , where C is capacitance, A is area and ε o is 8.85 x 10 -12 F/m. The thickness of the plain epoxy coating was measured to be approximately 35 μm and the area of the exposed coating was 5.55 cm 2 . Assuming the increase in capacitance during initial exposures up to 2 days is due to diffusional water uptake, the capacitance vs. t 1/2 curve was extrapolated to obtain the capacitance of the epoxy coating before exposure (t=0). The capacitance of the unpigmented epoxy coating was found to be 7.8715 x 10 -11 F/cm 2 . The dielectric constant of the epoxy coating was found to be 3.1 which lies in the range of dielectric constants of polymers of 3 – 10 [108]. The thickness of 5 wt% Ce bentonite pigment loaded epoxy coating was measured to be 55 μm and the capacitance of 5 wt% Ce bentonite pigment loaded epoxy coating was determined to be 2.162 x 10 -9 F/cm 2 . This gave a dielectric constant 130.43, which suggests that this value of capacitance does not correspond to that of the coating. Therefore, this implies that the high frequency capacitive response from the bentonite coatings except 5LaB.Ep was from the mixed capacitances of the coating and defects in the coating. It has to be noted that, despite bentonites degrading the barrier properties, Zn bentonite and La bentonite performed comparably to SrCr.Ep. 158
|Z| at 0.01 Hz (ohm.cm 2 ) |Z| at 0.01 Hz (ohm.cm 2 ) Coating capacitance (F.cm -2 ) Unpigmented.Ep SrCr.Ep 5ZnB.Ep 5CeB.Ep 5PrB.Ep 5LaB.Ep 10 -7 10 6 10 -8 10 5 10 7 0 100 200 300 400 500 600 700 Immersion time (h) 10 -9 10 -10 10 -6 0 100 200 300 400 500 600 700 Immersion time (h) Unpigmented.Ep SrCr.Ep 5ZnB.Ep 5CeB.Ep 5LaB.Ep 5PrB.Ep (a) (b) Figure 3.40. (a) Total impedance (b) Capacitances of epoxy coatings pigmented with exchange bentonites and SrCr.Ep standard, subject to static immersion in 0.5 M NaCl. The pigment loading levels of Zn bentonite pigment added to the epoxy was increased from 5 wt% to 30 wt% and its effect on the coating characteristics were investigated. SrCr.Ep was used as the positive control and unpigmented.Ep was used as the negative control. All the pigmented bentonite coatings exhibited a two time constant behavior and they were fit using the simplified equivalent circuit. Figure 3.41 shows the variation in the magnitude of total impedance at low frequency of Zn bentonite coatings relative to the SrCr.Ep standard. Increasing the pigment loadings up to 30 wt% from 5 wt% decreased the total impedance by about two orders of magnitude, much similar to the case observed in increasing Zn bentonite loadings in PVB coatings. Release of Zn 2+ cation was observed as the solution at the coating turned cloudy with the hydrolysis of the Zn 2+ cation at localized defects. However, it was different from the PVB case that the release of the cations was suppressed in the PVB resin due to no water uptake. It could be that, increasing the pigment concentrations in epoxy, increases the total number of localized defects in the coating. Hence, even though release is seen, significant destruction of barrier properties causes increased localized attack. 10 7 0 50 100 150 200 250 300 350 10 6 10 5 5ZnB.Ep 10ZnB.Ep 20ZnB.Ep 30ZnB.Ep Neat Ep SrCr.Ep 10 4 Immersion time (h) Figure 3.41. Total impedance of epoxy coatings pigmented with 5 to 30 wt% of Zn bentonite and SrCr.Ep standard, during static immersion in 0.5 M NaCl. 159
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FINAL REPORT Scientific Understandi
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This report was prepared under cont
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List of Acronyms AES Atomic Emissio
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List of Figures Figure 1.1. Figure
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Figure 1.21. Figure 1.22. Figure 1.
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Figure 3.11. Cathodic polarization
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Figure 4.12. Average Roughness of R
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Figure 5.4. Figures 5.5. Apparatus
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Figure 5.36. Figure 5.37. R paramet
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Figure 6.23. Two commercial samples
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Figure 7.1. a) instrumental configu
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List of Tables Table 1.1. Table 1.2
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Table 6.4. Processing parameters fo
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Keywords 1. Al alloys 2. Non-chroma
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1. Executive Summary This report su
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the role of electrophoresis in inhi
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occurring at low pHs and release at
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were obtained by a post treatment w
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4. G.O. Ilevbare, J.R. Scully, J. Y
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3. Objective The primary objective
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5. Results and Accomplishments In t
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powder, slurried with ultrapure wat
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TCP-coated AA2024-T3. A Kratos AXIS
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X-ray Photoelectron Spectroscopy (X
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Potential (V vs. Ag/AgCl) -0.2 -0.3
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Signal Intensity (counts/s) assessi
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Al (including both Al 0 and Al 3+ c
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TEM or during sample preparation, s
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Potential (V vs. Ag/AgCl) and uncoa
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5.1.4.8 Effects of Aging on the Fil
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Intensity (counts/s) Concentration
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|Z| 0.01Hz (ohm cm 2 ) |Z| 0.01Hz (
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The artificial scratch cell was als
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Raman intensity, a.u. 4000 880 3500
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Figure 1.24. Raman spectra for the
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peak at 520 cm -1 and an intense Cr
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Figure 1.28. Plots of the intensity
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Figure 1.30. (A) Video micrograph o
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The Zr and O signals arise from the
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Figure 1.35. (A) Corrosion potentia
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Table 1.1. Corrosion current (i cor
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additional pitting. The TCP coating
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Figure 1.41. Cr(VI) peak intensity
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Work is ongoing to understand how t
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9. L. Li, D-Y. Kim and G. M. Swain,
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carefully rinsed with DI water, air
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decrease to a net anodic current in
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Potential (mV vs. SCE) Potential (m
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i (A/cm 2 ) Immediately after silic
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Potential (mV vs. SCE) Rp (ohm.cm 2
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2.4.4 In situ AFM Scratching Result
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Figure 2.31. In situ AFM scratching
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(2.3) Figure 2.35. Specie diagram f
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concentration and the silicon to ca
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analysis coupled with XPS revealed
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5.2.4.4 In Situ AFM Scratching Befo
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esults in the formation of silicate
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26. P. Schmutz and G.S. Frankel, J.
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Pr 3+ , Y 3+ showed [12] an order o
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0.1M NaCl solution with varying con
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8.7 through pH 12.6 due to the lowe
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(b) (c) 99
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immersed in Ce 3+ remained bright w
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S phase and dissolution of Al matri
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Corrosion rate, i corr (A/cm 2 ) 6x
Page 141 and 142: I L (microA) 600 500 400 300 NC (-8
Page 143 and 144: than that of chromate[35]. Historic
Page 145 and 146: coupon was immersed with the polish
Page 147 and 148: 5.3.2.4 Results 5.3.2.4.1 Speciatio
Page 149 and 150: (c) Figure 3.8. Speciation diagram
Page 151 and 152: E vs. SCE (V) -0.70 -0.75 -0.80 -0.
Page 153 and 154: E vs. SCE (V) 1000 rpm E vs. SCE (V
Page 155 and 156: Chemical quantification showed a me
Page 157 and 158: (a) (b) Figure 3.15. (a) (top) SEM
Page 159 and 160: E vs. SCE (V) E vs. SCE (V) E vs. S
Page 161 and 162: -Z" (ohm) -Z" (ohm) -Z" (ohm) -Z" (
Page 163 and 164: (Figure 3.8b). However, no effect o
Page 165 and 166: CPS CPS CPS x 2 14 10 12 10 8 6 4 2
Page 167 and 168: CPS CPS 100 95 90 85 80 75 70 x 10
Page 169 and 170: I k L 0. 2 1 2 AnFC B D 2 3 O 1
Page 171 and 172: i -800 (A/cm 2 ) 10 -4 NaCl NaCl+5
Page 173 and 174: Corrosion rate ( 1/R p ) ohm -1 cm
Page 175 and 176: particles compared to zinc-free sol
Page 177 and 178: and Zn bentonite compounds have red
Page 179 and 180: 2) Deoxidizing for 3 minutes in an
Page 181 and 182: Scintag (now ThermoARL) Pad-V TM an
Page 183 and 184: Table 3.5. Characterization of bent
Page 185 and 186: Zn 2+ cation release (meq/100g) Pr
Page 187 and 188: (a) (b) (c) Figure 3.33. (a) An exp
Page 189 and 190: |Z| (ohm) Phase angle (degrees) 5.3
Page 191: |Z| at 0.01 Hz (ohm.cm 2 ) Pore Res
Page 195 and 196: pigmented coatings exhibited partia
Page 197 and 198: 5.3.3.6 Conclusions 1. Exchange ben
Page 199 and 200: 39. M. Mahdavian and M. M. Attar, P
Page 201 and 202: 100. F.Liebau, Structural Chemistry
Page 203 and 204: of the coated sample, which is tigh
Page 205 and 206: Lubricant Blue (Struers) was used f
Page 207 and 208: good grip on the dolly, the equipme
Page 209 and 210: Pressure (kPa) r (mm) Pressure x Ra
Page 211 and 212: Pressure x Radius (kN/m) plateau bu
Page 213 and 214: Pressure x Radius (kN/m) Pxr (KN/m)
Page 215 and 216: Average Roughness (m) In contrast,
Page 217 and 218: Adhesion Strength (J/m 2 ) PVB PVB
Page 219 and 220: Pressure (kPa) Constant Infusion up
Page 221 and 222: (a) (b) (c) (d) Figure 4.19. Coatin
Page 223 and 224: Min. Potential (V vs SHE) Min. Pote
Page 225 and 226: Pressure (kPa) exposure in hot wate
Page 227 and 228: Engineering Stress (MPa) slope of t
Page 229 and 230: Adhesion Strength (J/m 2 ) ASTM D33
Page 231 and 232: Pressure (kPa) Pressure (kPa) Radiu
Page 233 and 234: Adhesion Strength (J/m 2 ) Pressure
Page 235 and 236: Table 4.7. Adhesion Strength values
Page 237 and 238: Non-Cl./Deox. No CC Cleaned/Deox. N
Page 239 and 240: 5.4.5 Conclusions and Implications
Page 241 and 242: 5.5 Task 5: Inhibitor Activation an
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solution for equilibration at contr
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Table 5.2. Techniques applied to sp
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The capacitance was determined by E
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combination with zinc molybdate, a
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Concentration, mmol / L Final pH te
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Alkaline affects praseodymium solub
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MoO 4 2- ) inhibition to the system
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Zinc molybdate is reported to be si
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The presence of a salt that has no
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This approach yields two figures of
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Inhibitor mapping of the Hentzen 16
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The molybdate loss in the strontium
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The capacitance dC is given by 0 (
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2 C( r, t) C( r )[1 r 2 exp( D nt
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-thea (degree) logIZI (Ohm-Cm 2 ) P
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Capacitance (F) respectively. The c
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Capacitance (F) Weight gain (g) For
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Normalized Capacitance Change Norma
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Potential V (Ag/AgCl) Corrosion rat
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5.5.4.7 Nanopore structure characte
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Normaalized Transport Rate (g/m^2_d
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S-Parameter S-Parameter Penetration
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S-Parameter S-Parameter Penetration
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R-parameter R-parameter Penetration
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5. T. M. Letcher, “Thermodynamics
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pigment of CaSiO 3 with initial pH
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allowed a comparison of the differe
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The solution resistance (R sol ) va
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Theta [degrees] theta |Z| [ohm] 10
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C [F/cm2] Rcorr [ohm*cm2] 7075-AHN
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C [F/cm 2 ] Rcorr [ohm*cm 2 ] Rcorr
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Visual TTF [hours] Table 6.2. Param
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of Metallast pre-treatment, which h
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Prediction of the TTF obtained by A
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5.6.2 Electrochemical Impedance Spe
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5.6.2.2.1 Coating system descriptio
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Table 6.4. Processing parameters fo
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population of total TTF vectors th
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components of the impedance and the
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Figure 6.17. EIS spectra for sample
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Figure 6.18. Kaplan-Meier survival
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Maximum c i range Maximum ci range
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The type and number of input neuron
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Predicted TTF The BFM method, intro
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The most significant variables to i
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5.6.3 Characterization of Pigment D
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of sputtering gold and carbon paint
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Figure 6.26. Cross-sectional view o
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Figure 6.28. EDX maps of primer cro
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Figure 6.31. EDX maps of primer cro
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In Figure 6.34, Ca and Si existed a
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Table 6.8. Average percentage resid
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strictly limited due to the barrier
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Figure 6.37. Coating systems in det
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Each corrosion volume of scribed ar
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Corrosion Area (mm 2 ) 1200 1000 80
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Corrosion Area (mm 2 ) Corrosion Ra
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Corrosion Rate (mm/yr) Corrosion Vo
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Corrosion Area (mm 2 ) corrosion ra
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corrosion rate (mm/yr) Corrosion Vo
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Corrosion Volume (mm/yr) Corrosion
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ate, PPG CA7233 coated samples had
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Appendix 6B Table 6B.1. Corrosion v
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Table 6B.3. Corrosion rate of sampl
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Table 6B.5. Corrosion area of sampl
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5.7. Task 7: Characterization of Lo
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at 65C. After using DI water to rin
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Transmission Mode Conduct EIS measu
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Cdl(F/cm 2 ) Rp(.cm 2 ) relatively
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pit bottom area (cm 2 ) pit bottom
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2days 2days 1mm 1mm 7days 7days Pit
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(a) (b) Si Si O Al Na Ca K Si Al-Cu
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Pit 1 and pit 2 as shown in Figure
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In these experiments, Deft primers
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For the case of as-deposited thin f
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3. L. Balazs, Physica E, 54, 1183-1
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and subsequently re-oxidized in two
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not represent true adhesion strengt
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• The pit morphology in 0.5 M NaC
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Appendix 2. List of Scientific/Tech
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“The Secret Life of Chromate Free
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