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performance for samples that failed during the length of exposure but it could not be used for samples that did not fail. The percentage of delaminated area A del was calculated using Equation 6.1.1 at the time when C dl showed an increase. Although both parameters are related, a clear correlation between the visual TTF and the A del cannot be extracted, suggesting that for the purpose of this experiment, the delaminated area method is also a weak parameter to measure coating performance. Artificial neural networks (ANN) were used to predict visual TTF based only on phase angle information. The predicted TTF values for the samples tested were calculated previously and can be seen in Table 6.2. The information obtained by ANN correlates with the visual TTF with an R 2 of 0.79, Figure 6.13. The value of R 2 was calculated for only the samples that failed before 720 hours as was done for C dl . Although the R 2 for ANN is smaller than that of C dl , ANN provided a correlation with the visual TTF even for samples that did not fail. Also, ANN parameter gave a predictive time to failure after finalization of the test where visual examination could only assess that the samples did not fail. From all the EIS parameters available to characterize coating degradation, R corr showed a weak correlation with visual TTF, C dl showed a strong correlation with samples that fail (TTF < 720 h) but was unsuccessful for samples that did not fail. ANN parameter, which it was explicitly derived to predict TTF based on phase angle information, showed the best correlation with all samples (failed or not) and therefore was selected as the parameter to characterize coating performance. A rank of the coating tested was obtained based on ANN parameter. Among all the samples tested Boegel 8500 conversion coating and Deft02GN084 showed the best performance with a predicted TTF of 1059 and those treated with Metallast and Sicopoxy 577-630 showed the worst performance. 5.6.1.5 Conclusions EIS combined with visual examination after accelerated salt spray exposure was used to analyze coating performance. A relationship between the chemical composition of the coatings and the coating performance was established. R corr , defined as the sum of the pore resistance, the r defect resistance together and the solution resistance was a weak predictor of coating performance in exposure testing. The metal-coating interface capacitance C dl parameter showed strong correlation with the visual TTF for only those samples that failed during exposure. The percentage of delaminated area %A del parameter showed weak correlation with the visual examination. 274
Prediction of the TTF obtained by ANN fed with phase angle information showed strong correlation with the visual TTF for all samples tested. A ranking among coatings was obtained using the ANN parameter. The combination of Boegel 8500 conversion coating with Deft02GN084 primer ranked first among the emerging corrosion resistance coatings tested. 5.6.1.6 References 1. Cohen, S. M., Review - Replacement for Chromium Pretreatments on Aluminum. Corrosion, 1995. 51(1): p. 71-78. 2. Sinko, John, Challenges of Chromate Inhibitor Pigments Replacement in Organic Coatings. Progress in Organic Coatings, 2001. 42: p. 267-282. 3. Kendig, M. W. and Buchheit, R.G., Corrosion Inhibition of Aluminum and Aluminum Alloys by Soluble Chromates, Chromate Coatings, and Chromate-Free Coatings. Corrosion, 2003. 59(5): p. 379-400. 4. Trabelsi, W., Triki, E., Dhouibi, L., et al., The use of pre-treatments based on doped silane solutions for improved corrosion resistance of galvanised steel substrates. Surface & Coatings Technology, 2006. 200(14-15): p. 4240-4250. 5. Dufek, E. J. and Buttry, D. A., Inhibition of O-2 reduction on AA2024-T3 using a Zr(IV)- Octadecyl phosphonate coating system. Electrochemical and Solid State Letters, 2008. 11(2): p. C9-C12. 6. Pearlstein, F and Agarawala, S, Trivalent Chromium Conversion Coating for Aluminum. US PATENT, 1994. 5,304,257. 7. Pearlstein, F. and Agarwala, V. S., Trivalent Chromium Solutions for Applying Chemical Conversion Coatings to Aluminum-Alloys or For Sealing Anodized Aluminum. Plating and Surface Finishing, 1994. 81(7): p. 50-55. 8. Hinton, B. R. W., Arnott, D. R., and Ryan, N. E., The Inhibitino of Aluminum-alloy Corrosion by Cerous Cations. Metals Forum, 1984. 7(4): p. 211-217. 9. Breslin, C.B. and Geary, M., Influence of Rare-Earth Metal Passivation Treatments on the Dissolution of Tin-Zinc Coatings. Corrosion 1998. 54(12): p. 964-970. 10. Aldykiewicz, A. J., Isaacs, H. S., and Davenport, A. J., The Investigation of Cerium as a Cathodic Inhibitor for Aluminum-Copper Alloys. Journal of the Electrochemical Society, 1995. 142(10): p. 3342-3350. 11. Buchheit, R.G., Mamidipally, S.B., Schmutz, P., et al., Active Corrosion Protection in Ce-Modified Hydrotalcity Conversion Coatings. Corrosion, 2002. 58(1): p. 3-14. 12. Nickerson, B.C., Matzdorf, C.A., and Lipnickas, E., Evaluation of Modified Zirconium Trivalent Chromium Conversion Coatings by Accelerated Corrosion and Electrochemical Techniques Tri-Service Corrosion Conference Proceedings, 2005. 13. Rudd, A.L., Breslin, C.B., and Mansfeld, F., The Corrosion Protection Afforded by Rare Earth Conversion Coatings Applied to Magnesium. Corrosion Science, 2000. 42: p. 275- 288. 14. ASTM, ASTM B117-03 Standart Practive for Operating Salt Spray (Fog) Apparatus, in Annual Book of ASTM Standards. 2003, ASTM: Philadelphia, PA. 15. ASTM, ASTM D5894 - Standard Practice for Cyclic Salt Fog/UV Exposure of Painted Metal, in Annual Book of ASTM Standards. 2005, ASTM: Philadelphia, PA. 275
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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
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I L (microA) 600 500 400 300 NC (-8
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than that of chromate[35]. Historic
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coupon was immersed with the polish
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5.3.2.4 Results 5.3.2.4.1 Speciatio
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(c) Figure 3.8. Speciation diagram
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E vs. SCE (V) -0.70 -0.75 -0.80 -0.
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E vs. SCE (V) 1000 rpm E vs. SCE (V
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Chemical quantification showed a me
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(a) (b) Figure 3.15. (a) (top) SEM
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E vs. SCE (V) E vs. SCE (V) E vs. S
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-Z" (ohm) -Z" (ohm) -Z" (ohm) -Z" (
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(Figure 3.8b). However, no effect o
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CPS CPS CPS x 2 14 10 12 10 8 6 4 2
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CPS CPS 100 95 90 85 80 75 70 x 10
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I k L 0. 2 1 2 AnFC B D 2 3 O 1
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i -800 (A/cm 2 ) 10 -4 NaCl NaCl+5
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Corrosion rate ( 1/R p ) ohm -1 cm
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particles compared to zinc-free sol
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and Zn bentonite compounds have red
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2) Deoxidizing for 3 minutes in an
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Scintag (now ThermoARL) Pad-V TM an
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Table 3.5. Characterization of bent
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Zn 2+ cation release (meq/100g) Pr
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(a) (b) (c) Figure 3.33. (a) An exp
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|Z| (ohm) Phase angle (degrees) 5.3
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|Z| at 0.01 Hz (ohm.cm 2 ) Pore Res
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|Z| at 0.01 Hz (ohm.cm 2 ) |Z| at 0
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pigmented coatings exhibited partia
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5.3.3.6 Conclusions 1. Exchange ben
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39. M. Mahdavian and M. M. Attar, P
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100. F.Liebau, Structural Chemistry
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of the coated sample, which is tigh
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Lubricant Blue (Struers) was used f
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good grip on the dolly, the equipme
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Pressure (kPa) r (mm) Pressure x Ra
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Pressure x Radius (kN/m) plateau bu
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Pressure x Radius (kN/m) Pxr (KN/m)
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Average Roughness (m) In contrast,
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Adhesion Strength (J/m 2 ) PVB PVB
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Pressure (kPa) Constant Infusion up
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(a) (b) (c) (d) Figure 4.19. Coatin
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Min. Potential (V vs SHE) Min. Pote
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Pressure (kPa) exposure in hot wate
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Engineering Stress (MPa) slope of t
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Adhesion Strength (J/m 2 ) ASTM D33
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Pressure (kPa) Pressure (kPa) Radiu
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Adhesion Strength (J/m 2 ) Pressure
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Table 4.7. Adhesion Strength values
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Non-Cl./Deox. No CC Cleaned/Deox. N
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5.4.5 Conclusions and Implications
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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
Page 257 and 258: Zinc molybdate is reported to be si
Page 259 and 260: The presence of a salt that has no
Page 261 and 262: This approach yields two figures of
Page 263 and 264: Inhibitor mapping of the Hentzen 16
Page 265 and 266: The molybdate loss in the strontium
Page 267 and 268: The capacitance dC is given by 0 (
Page 269 and 270: 2 C( r, t) C( r )[1 r 2 exp( D nt
Page 271 and 272: -thea (degree) logIZI (Ohm-Cm 2 ) P
Page 273 and 274: Capacitance (F) respectively. The c
Page 275 and 276: Capacitance (F) Weight gain (g) For
Page 277 and 278: Normalized Capacitance Change Norma
Page 279 and 280: Potential V (Ag/AgCl) Corrosion rat
Page 281 and 282: 5.5.4.7 Nanopore structure characte
Page 283 and 284: Normaalized Transport Rate (g/m^2_d
Page 285 and 286: S-Parameter S-Parameter Penetration
Page 287 and 288: S-Parameter S-Parameter Penetration
Page 289 and 290: R-parameter R-parameter Penetration
Page 291 and 292: 5. T. M. Letcher, “Thermodynamics
Page 293 and 294: pigment of CaSiO 3 with initial pH
Page 295 and 296: allowed a comparison of the differe
Page 297 and 298: The solution resistance (R sol ) va
Page 299 and 300: Theta [degrees] theta |Z| [ohm] 10
Page 301 and 302: C [F/cm2] Rcorr [ohm*cm2] 7075-AHN
Page 303 and 304: C [F/cm 2 ] Rcorr [ohm*cm 2 ] Rcorr
Page 305 and 306: Visual TTF [hours] Table 6.2. Param
Page 307: of Metallast pre-treatment, which h
Page 311 and 312: 5.6.2 Electrochemical Impedance Spe
Page 313 and 314: 5.6.2.2.1 Coating system descriptio
Page 315 and 316: Table 6.4. Processing parameters fo
Page 317 and 318: population of total TTF vectors th
Page 319 and 320: components of the impedance and the
Page 321 and 322: Figure 6.17. EIS spectra for sample
Page 323 and 324: Figure 6.18. Kaplan-Meier survival
Page 325 and 326: Maximum c i range Maximum ci range
Page 327 and 328: The type and number of input neuron
Page 329 and 330: Predicted TTF The BFM method, intro
Page 331 and 332: The most significant variables to i
Page 333 and 334: 5.6.3 Characterization of Pigment D
Page 335 and 336: of sputtering gold and carbon paint
Page 337 and 338: Figure 6.26. Cross-sectional view o
Page 339 and 340: Figure 6.28. EDX maps of primer cro
Page 341 and 342: Figure 6.31. EDX maps of primer cro
Page 343 and 344: In Figure 6.34, Ca and Si existed a
Page 345 and 346: Table 6.8. Average percentage resid
Page 347 and 348: strictly limited due to the barrier
Page 349 and 350: Figure 6.37. Coating systems in det
Page 351 and 352: Each corrosion volume of scribed ar
Page 353 and 354: Corrosion Area (mm 2 ) 1200 1000 80
Page 355 and 356: Corrosion Area (mm 2 ) Corrosion Ra
Page 357 and 358: 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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