Surface reactivation treatment

Abstract

The present disclosure relates to a method of reactivating the surface of an organic paint coating, a method of facilitating adhesion of a further coating to the organic paint coating, and a substrate having a reactivated organic paint coating. There is also disclosed a surface reactivation treatment for an organic paint coating. The reactivation method also facilitates adhesion of the organic paint coating to further coating(s) across a broad application window.

Claims

1. A method of reactivating a surface of an organic paint coating present on a substrate, the method comprising: applying, at a humidity of less than 5 millibar (mb) partial water vapor pressure at a temperature of about 10° C. to 35° C., a surface treatment to the organic paint coating, the surface treatment consisting of a solvent, an organic nanoparticle, optionally an additive, and a surface exchange agent selected from the group consisting of a titanate, zirconate, and chelates thereof, wherein the organic nanoparticle is carbon black having a particle size of between about 1 and about 160 nm.

2. A method of facilitating adhesion of a coating to an organic paint coating disposed on a substrate, the method comprising: applying, at a humidity of less than 5 millibar (mb) partial water vapor pressure at a temperature of about 10° C. to 35° C., a surface treatment to the organic paint coating to form a reactivated organic paint coating, the surface treatment consisting of a solvent, an organic nanoparticle, optionally an additive, and a surface exchange agent selected from the group consisting of a titanate, zirconate, and chelates thereof, wherein the organic nanoparticle is carbon black having a particle size of between about 1 and about 160 nm; and depositing a second coating on the reactivated organic paint coating.

3. The method according to claim 1, wherein the solvent, agent, organic nanoparticle, and additive, are applied as a single mixture to the organic paint coating.

4. The method according to claim 1, wherein the solvent is an organic solvent selected from a ketone, alcohol, ether, or combinations thereof.

5. The method according to claim 4, wherein the organic solvent is a glycol, glycol ether, alcohol, glycol monoether alcohol, or combinations thereof.

6. The method according to claim 5, wherein the organic solvent is an ether:alcohol combination that is a glycol diether:C.sub.1-6 alcohol or C.sub.1-4 alcohol.

7. The method according to claim 6, wherein the glycol diether is dipropylene glycol dimethyl ether and the C.sub.1-4 alcohol is isopropanol and/or n-propanol.

8. The method according to claim 1, wherein the solvent is present in an amount from about 90% to about 99% based on total weight of the surface treatment.

9. The method according to claim 1, wherein the surface exchange agent is a C.sub.1-10 alkyl titanate, a C.sub.1-10 alkyl zirconate, or a chelate thereof.

10. The method according to claim 9, wherein the C.sub.1-10 alkyl titanate or a chelate thereof is tetra-n-propyltitanate or the C.sub.1-10 alkyl zirconate or a chelate thereof is tetra-n-propylzirconate.

11. The method according to claim 1, wherein the surface exchange agent is present in an amount from about 1% to about 8% based on total weight of the surface treatment.

12. The method according to claim 1, wherein the organic nanoparticle is present in an amount of less than about 0.5% based on total weight of the surface treatment.

13. The method according to claim 1, wherein the surface treatment consists of the solvent, organic nanoparticle, additive, and surface exchange agent.

14. The method according to claim 1, wherein the additive is selected from the group consisting of rheology modifier, wetting agent, surfactant, dispersant, anti-foaming agent, levelling agent, colorant, anti-corrosion agent, and combination(s) thereof.

15. The method according to claim 1, wherein the additive is selected from the group consisting of colorant, anti-corrosion agent, and combination(s) thereof.

16. The method according to claim 1, wherein the additive is present in an amount of less than about 10% based on total weight of the surface treatment.

17. The method according to claim 1, wherein the formulation is a solution or emulsion.

18. The method according to claim 1, wherein the substrate is a substantially inelastic panel.

19. The method according to claim 1, wherein the substrate is a metal, metal alloy, or composite material.

20. The method according to claim 1, further comprising drying the surface of the organic paint coating.

21. The method according to claim 1, wherein color shift (ΔE) of the organic paint coating is less than 1 when measured after a second coating has been applied to the surface of the organic paint coating.

22. The method of claim 1, wherein the surface treatment comprises the organic nanoparticle in an amount of about 0.01% to about 1% based on total weight of the surface treatment.

23. The method of claim 22, wherein the surface treatment comprises the organic nanoparticle in an amount of about 0.01% to about 0.5% based on total weight of the surface treatment.

24. The method of claim 1, further comprising cleaning the organic paint coating after applying the surface treatment to the organic paint coating.

25. The method of claim 2, further comprising cleaning the organic paint coating after applying the surface treatment to the organic paint coating.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) In the examples, reference will be made to the accompanying drawings, wherein:

(2) FIG. 1 is a schematic representation of a panel section of an in service aged organic paint coating previously adhered to and present on a substrate of a panel section that is treated for reactivation of its surface adhesion properties to facilitate adhering a further organic coating onto the in service aged organic paint coating without damaging the integrity of that in service aged organic paint coating to the substrate.

(3) FIG. 2 highlights visual representations relating to a scale of 1 to 10 corresponding to maximum tear length and % area of coating removed under rain erosion testing.

(4) FIG. 3 is images illustrating the amount of gray paint removed from white paint using Single Impact Jet Apparatus (SIJA) techniques with and without different surface treatments. Note that large amounts of paint removal indicate poor adhesion; less paint removal indicates better adhesion. The images demonstrate: Significant gray paint removal without reactivation treatment at low humidity (4.2 mb partial water vapor pressure). Low gray paint removal when the white coating is reactivated under higher humidity (10.1 mb partial water vapor pressure) using AT-1 Higher relative gray paint removal when the white coating is reactivated under low humidity using AT-1 Less gray paint removal under low humidity when AT-1 is modified to include nanoparticles

(5) FIG. 4 is images illustrating Single Impact Jet Apparatus results demonstrating different amounts of gray paint removal from white paint under low humidity (3.0 to 3.5 mb partial water vapor pressure) conditions. The results demonstrate: Significant gray paint removal without reactivation treatment at low humidity Low gray paint removal when the white coating is reactivated under higher humidity (10.1 mb partial water vapor pressure) using AT-1, Higher relative gray paint removal when the white coating is reactivated under low humidity using AT-1 Less gray paint removal when AT-1 is modified to include nanoparticles

(6) FIG. 5 is images illustrating Single Impact Jet Apparatus results demonstrating paint removal from white paint under high humidity (10.3 mb partial water vapor pressure) conditions. The results demonstrate: Without reactivation significant gray paint is removed at high humidity Reactivation conducted at high humidity conditions using AT-1 is effective in improving adhesion of the gray coat to the white coat Inclusion of carbon black to the treatment does not negatively affect the gray coating adhesion when reactivation is conducted under high humidity conditions and produces results similar to AT-1.

(7) FIG. 6 is images illustrating Single Impact Jet Apparatus (SIJA) results demonstrating the amount of gray paint removed from white paint with and without different surface treatments. Note large amounts of paint removal indicate poor adhesion; less paint removal indicates better adhesion. The images demonstrate: Significant gray paint removal without treatment at low humidity (4.2 mb partial water vapor pressure) Low gray paint removal when the white coating is reactivated under higher humidity (10.3 mb partial water vapor pressure) using AT-1 Higher relative gray paint removal when the white coating is reactivated under low humidity (4.2 mb partial water vapor pressure) using AT-1 Less gray paint removal under low humidity (4.2 mb partial water vapor pressure) when AT-1 is modified to include nanoparticles

(8) FIG. 7 is Scanning Electron Microscope images showing residue morphology of AT-1 reactivation treatment with no added nanoparticles when applied under high (38% RH, 68° F.; 8.9 mb) and low humidity (13% RH, 66° F.; 2.7 mb) conditions to DHS CA8000/BAC70846 with 4:1 (C:C2) thinner. The images demonstrate: High humidity application produces fine, textured, open (porous) structure of residue Low humidity application produces a more continuous, smooth, gel-like (less porous) structure of residue

(9) FIG. 8 is Scanning Electron Microscope images showing residue morphology of AT-1 reactivation treatment with 0.005 wt % Special Black 5 (50 nm) nanoparticles added when applied under high and low humidity conditions. The images demonstrate: High humidity application produces fine, textured, open (porous) structure of residue similar to that in FIG. 7 Low humidity application produces a somewhat more texture open structure than that in FIG. 7

(10) FIG. 9 is Scanning Electron Microscope images showing AT-1 reactivation treatment with 0.01 wt % Special Black 5 (50 nm) nanoparticles added residue morphology when applied under high and low humidity conditions. The images demonstrate: High humidity application produces fine, textured, open (porous) structure of residue similar to that in FIG. 7 Low humidity application produces a somewhat more texture open structure than that in FIG. 7

(11) FIG. 10 is Scanning Electron Microscope images showing AT-1 reactivation treatment with 0.05 wt % Special Black 5 (50 nm) nanoparticles added residue morphology when applied under high and low humidity conditions. The images demonstrate: High humidity application produces fine, textured, open (porous) structure of residue similar to that in FIG. 7 Low humidity application produces a somewhat more texture open structure than that in FIG. 7

(12) FIGS. 11-13 are whirling arm rain erosion results demonstrating different amounts of blue paint removal using different surface treatments applied under low humidity conditions. The images demonstrate: Significant blue paint removal without reactivation treatment. Less paint removal relative to no treatment when the white coating is reactivated with AT-1. Even less paint removal when AT-1 is modified to include nanoparticles.

EXAMPLES

(13) Aspects of the present disclosure will now be described with reference to the following non-limiting examples. Details of the products mentioned by trade names in the examples are as follows:

(14) Al 2024-T3 clad—[Grade of Aluminum typically used in aerospace applications]

(15) Ardrox 1250—[Mildly acidic cleaning material containing hydroxyethane phosphonic acid, potassium hydroxyethane phosphonate, and primary alcohol ethoxylate; from Chemetall]

(16) AC-131-CB—[Non-chromated conversion coating (water based, zirconium n-propoxide, 3-glycidoxypropyl) trimethoxysilane solgel) for metals like Aluminum, 3M]

(17) PPG Desothane HS/DHS—[High solids Polyurethane coating, PPG Aerospace PRC-DeSoto]

(18) CA8000/B7084X—[White Polyurethane base component of PPG Desothane HS/DHS coating, PPG Aerospace PRC-DeSoto]

(19) CA8000/B707X—[Gray Polyurethane base component of PPG Desothane HS/DHS coating, PPG Aerospace PRC-DeSoto]

(20) CA8000/B50103X—[Blue Polyurethane base component of PPG Desothane HS/DHS coating, PPG Aerospace PRC-DeSoto]

(21) CA8000C—[Organic thinner component of PPG Desothane HS/DHS coating. Referred to as “C” in examples]

(22) CA8000C2—[Organic thinner component of PPG Desothane HS/DHS coating containing added coating organotin catalyst. Referred to as “C2” in examples]

(23) AT-1—[Tetra-n-propylzirconate in dipropylene glycol dimethyl either/n-propanol solvent reactivator supplied by Zip-Chem as Sur-Prep AP-1]

(24) Inorganic nanoparticles listed on page 13 and Tables 1 and 2 have been sourced from BYK Additives & Instruments or Sigma Aldrich. Carbon Black (such as Special Black 5 and Special Black 100) was sourced from Evonik Degussa.

(25) Nanoparticles used in the non-limiting Examples 1 to 14 were sourced as indicated in the below:

(26) TABLE-US-00003 Particle Particle Used in size Surface Solids Density Examples Product (nm) Particle Treatment (Wt %) (gm/ml) Solvent 7 BYK 80 Silicon polysiloxane 30 1.14 methoxy propylacetate/ LP-X-21193 oxide (linear, med methoxy propanol polar)  8, 13 BYK 160 Silicon polysiloxane 70 1.88 methoxy propylacetate/ Nanobyk 3652A oxide (linear, med methoxy propanol polar)  6, 14 BYK 10 Aluminum polyester 30 1.24 methoxy propylacetate/ LP-X-21441 oxide based block methoxy propanol copolymer 9, 10, 14 BYK 40 Aluminum polyester 50 1.53 methoxy propylacetate/ LP-X-20693 oxide based block methoxy propanol copolymer 11, 12 Aldrich <50 Aluminum unknown 20 0.79 isopropanol 702129 oxide 1 Evonik Degussa 35 Carbon Unknown 100 None Printex XE 2B Black 2, 3 Evonik Degussa 50 Carbon Unknown 100 None Special Black 5 Black 2, 3 Evonik Degussa 20 Carbon Unknown 100 None Special Black Black 100 4 Aldrich <100 Zirconium Unknown 100 None 544760 oxide 14  BYK 20 Silicon polysiloxane 25 methoxy propylacetate/ Nanobyk 3652 oxide (linear, med methoxy propanol polar)

(27) The following procedure was used to prepare the examples for testing.

(28) Prepare Substrate SIJA Panels/Rain Erosion Foils

(29) The substrates used in the examples were Al 2024-T3 clad, although the substrate can be readily varied to other metals, metal alloys or a composite material, or other substantially inelastic or rigid substrate as previously described.

(30) For aluminum substrate: a. Clean. Cleaning may be done with i) a rubbing solvent such as methyl propyl ketone with a wiper onto the surface and then drying thoroughly with clean wipers and or ii) by using an alkaline cleaner such as Chemetall Pace B-82 and rubbing with a very fine abrasive pad such as 3M Scotchbrite™ #7447 followed by thorough rinsing to remove residue. b. Deoxidize. Deoxidation may be done by i) abrading with a very fine abrasive aluminum oxide pad and rinsing the residual abrasive powder off with copious quantities of water or ii) by applying an acid cleaner such as Ardrox 1250 by Chemetall, keeping the panel wet for 10 to 20 minutes, and then rinsing with copious quantities of water. c. Apply a conversion coat. The conversion coat may contain corrosion inhibitors. The conversion coat used here was AC-131-CB by 3M. Conversion coat should be applied by the manufacturer's instructions.

(31) Apply Primer

(32) For composite or aluminum, application of common aerospace epoxy based primer optionally incorporating additives to aid corrosion resistance at 0.4 mil (10 micron) to 1.5 mil (38 microns) dry film thickness (dft) per manufacturer instructions at 65° F. to 85° F. at 30-60% RH and cure at ambient conditions for 1 to 24 hours. All panels/foils used in testing were aluminum.

(33) Prepare First Organic Paint Coating (First Topcoat)

(34) Apply polyurethane topcoat (e.g.: PPG Desothane HS topcoat containing CA8000/B70846X base—white color of this topcoat also designated as BAC 70846, thinners used include PPG Aerospace PRC-DeSoto Desothane HS CA8000C and CA8000C2 thinner components. Activator component is CA8000B) a. At 2.0 to 4.0 mils (50 to 100 microns). Application is typically at 65° F. to 95° F., generally at about 75 F, and at relative humidity at up to 70% RH. Application is generally using HVLP spray gun, such as a Binks M1-H HVLP gun with a 92 to 94 nozzle or DeVilbiss Compact Gravity with a 1.4 tip. b. Flash first topcoat. Solvent is flashed off of topcoat panels/foils, typically for one hour and at same conditions as topcoat application. c. Cure first topcoat. Top coated panels/foils are cured under conditions indicated in examples. These conditions are typically 120 F with relative humidity between 3 and 18% RH followed by a post cure that is typically at ambient conditions (eg. 75 F and 30 to 60% RH) for between 1 day and 14 days.

(35) Tape First Topcoat i. SIJA panels: The first topcoat was over-coated with promoter and the second topcoat following taping through the middle of the coupon with 3M vinyl tape (#471) to form a paint edge on its removal. This edge was the impact target for SIJA (Single Impact Jet Apparatus) analysis. ii. Rain erosion foils: Following cure of the first topcoat layer, the front (bullnose) of the foils were masked (Intertape Polymer Group, PG-777 tape) prior to over-coating. After the overcoat was applied and cured, the tape was removed.

(36) Prepare Reactivation Treatment a. Mix reactivation treatment. Four methods: Method i and ii were used if nanoparticles came in powdered form. Method iii and iv were used if nanoparticles are in pre-dispersed form. Carbon black organic powder nanoparticles used methods i and ii. Zirconium oxide inorganic nanoparticles used method i. Pre-dispersed inorganic particles used methods iii and iv. AT-1 was made using 1-8% surface exchange or transesterification agent such as zirconates or titanates, in an alcohol:dipropylene glycol dimethyl ether solvent mix. Typical preparation of AT-1 involves preparing two solutions (Part A and Part B) which are mixed together prior to application. Part B typically contains an ether/alcohol solvent mix, while Part A includes the surface or transesterification agent dissolved in an alcohol. The solvents used are anhydrous, although water present in the solvent can be tolerated without loss of activity of the treatment as long as water is present in minor amounts, for example trace amounts of up to 800 ppm for the present zirconates or titanates. Part A and Part B are combined prior to application (with shaking/stirring), and the nanoparticles added either to part A or Part B prior to combining the two parts, or to premixed Part A and part B as described below; i. Powdered form: Disperse nanoparticles into AT-1 and sonicate for 1-5 minutes to ensure “bundles” of carbon black or zinc oxide powder nanoparticles are dispersed. This was done by placing sealed glass vial containers into ultrasound water bath at room temperature and then turning on the bath. ii. Powdered form: Disperse nanoparticles in part B of AT-1 with ultrasound for 1 to 5 minutes. Then add AT-1 part A into Part B with no ultrasound, just shaking or mixing for at least one minute. iii. Pre-dispersed form: Add pre-dispersed nano-particles into AT-1 and shake by hand or mixer for at least one minute. iv. Pre-dispersed form: Add pre-dispersed nano-particles to Part B of AT-1 and shake by hand or mixer for at least one minute. Then add Part A of AT-1 into Part B and shake by hand or mixer for at least one minute. b. Apply reactivation treatment. No cleaning or washing of the first topcoat or any other pre-treatment or reactivation treatment is necessary prior to application of the reactivation treatment. Reactivation treatment applied at 68° F. to 77° F. at water vapour pressures and relative humidity indicated in the examples (typically at water vapour pressure of less than 5 mb corresponding to relative humidities of around 20% or less at 70° F.). Application is generally using HVLP spray gun, such as Binks M1-H HVLP gun with a 92 or 94 nozzle or Devilbiss Compact Gravity with a 1.4 tip. c. Dry reactivation treatment. Reactivation treatment typically dried for 2 hours (30 minutes to 1 day) at temperature and relative humidity of reactivation treatment application as indicated in the example.

(37) Prepare Further Coating (Second Topcoat) a. Apply overcoat. Application of polyurethane topcoat (e.g.: PPG Desothane HS topcoat containing CA8000/1350103X base—blue color of this topcoat also designated as BAC 50103 or PPG Desothane HS topcoat CA8000/13707X base gray) at 3.5 to 5.0 mils (85 to 125 microns). Application is typically at 65° F. to 85° F., generally at about 75° F., and at relative humidity typically the same as the promoter application. Application is generally using HVLP spray gun, such as Binks M1-H HVLP gun with a 92 or 94 nozzle or DeVilbiss Compact Gravity with a 1.4 tip. b. Flash second topcoat. Solvent is flashed off of topcoat panels/foils, typically for one hour and at same conditions as second topcoat application. c. Cure second topcoat. Top coated panels/foils are cured under conditions indicated in examples. These conditions are typically at 120° F. with relative humidity between 3 and 18% RH at 120° F. for 3 to 24 hours. The post cure is typically at ambient conditions (e.g. 75° F. and 30 to 60% RH) for between 7 and 14 days prior to testing.

(38) Remove Tape prior to testing from SIJA panels/rain erosion foils.

(39) Adhesion Test Methods

(40) The table below details the equipment and conditions used for testing

(41) TABLE-US-00004 Equipment Conditions. SIJA Adhesion testing was completed using a Single Impact Jet SIJA Apparatus (SIJA, Cambridge). The initial equipment was typically configured using a 0.8 mm nozzle and employed 0.22 calibre 5.5 mm Crosman Accupell Pointed Pellets (#11246). Testing was completed following immersion in water for 16 to 18 hours, employing a line laser to locate the impact position, and using a 45° specimen to impact droplet geometry. Surface water was then removed by lightly wiping with a clean wiper. A single water jet was employed at each site to test adhesion. The nominal velocity of each individual shot was recorded next to the impact site for future reference. The impact velocity employed was 600 ± 25 m/s. In some examples, the amount of overcoat removed, and hence the inter-coat adhesion, was assessed employing image analysis techniques to quantify the area of paint removed. The more overcoat removed corresponded with inferior inter-coat adhesion. Whirling Rain erosion testing was completed on a whirling arm rain erosion apparatus Arm Rain employing a 1.32 m (52 inch) zero lift helicopter like propeller run at 3600 rpm. Erosion The foils were attached to the propeller at a distance along the propeller Testing correlating to a velocity of 170 ms.sup.−1 (380 mile per hour) at the midpoint of the foil. The effective rain field density of 2 mm droplets used during the experiment was 2.54 × 10.sup.−5 kmh.sup.−1 (1 inch per hour). After 30 minutes, the impact of rain erosion on the inter-coat adhesion of the foils was evaluated according to the amount of paint removed or tear lengths. The impact of water droplets on the leading edge of the over-coat formed on removal of the tape during the experiment erodes the over-coating layer relative to the strength of inter-coat adhesion.

Examples 1 to 13

(42) Table 1 below sets out the test results of Examples 1 to 4. All coupons were tested in Singe Impact Jet Apparatus (SIJA)

(43) TABLE-US-00005 TABLE 1 Temperature/% Relative Humidity of Reactivation Ex. FIG. Treatment Application No. Nanoparticles Paint System No. (Water vapor pressure in mb) 1 Carbon Black First Topcoat: DHS CA8000 BAC 70846 3 Low humidity: Average white (4:1 PPG Aerospace PRC-DeSoto 68° F., 18% RH (4.2 mb) particle size Desothane HS CA8000C:CA8000C2 High humidity: 35 nm thinner components); cured 16 hours 68° F., 44% RH (10.3.mb) at 120° F., 3% RH, then 24 hours at 75° F., 12% RH Second Topcoat: DHS CA8000 BAC 707 gray (C thinner) cured 72 hours at 120° F., 3% RH 2 Carbon Black First Topcoat: DHS CA8000 BAC 70846 4 Low humidity: Average white, (4:1 PPG Aerospace PRC-DeSoto 70° F., 12-14% RH (3.0 to 3.5 particle size Desothane HS CA8000C:CA8000C2 mb) 50 nm thinner components); cured 16 hours High humidity: at 120° F., 3% RH then 24 hours at 75° F., 68° F., 43% RH (10.1 mb) 12% RH Average Second Topcoat: DHS CA8000 BAC707 particle size gray (C thinner) cured 72 hours at 20 nm 120° F., 8-12% RH 3 Carbon Black First Topcoat: DHS BAC 70846 (C 5 68° F., 43% RH (10.1 mb) Average thinner); cured 16 hours at 120° F., 18% particle size RH then 69 hours at 75° F., 70% RH 50 nm Average Second Topcoat: DHS BAC 707 (C particle size thinner); cured 3 days at 120° F. in 20 nm oven. 4 Zirconium First Topcoat DHS BAC 70846 (4:1 C:C2 6 Low humidity oxide thinner) cured 16 hours at 120° F., 3% 68° F., 18% RH (4.2 mb) Average RH, then 24 hours at 75° F., 12% RH High humidity particle size Second Topcoat DHS BAC707 (C 68° F. 44% RH (10.3 mb) 50 nm thinner); cured 3 days at 120° F. in oven

(44) Table 2 below sets out the test results of Examples 5 to 13. All reactivation treatments are applied at 76.5° F., 9.4% RH (2.9 mb). All foils were tested in Whirling Arm Rain Erosion.

(45) TABLE-US-00006 TABLE 2 Ex. Max Tear Results No. Nanoparticle Paint System in 1/32 inch)* 5 a) None DHS 70846 white (4:1 C:C2 thinner); Example 5a) No Sand: 80 b) AT-1 (standard cured at 120° F., 3% RH for 96 hours Example 5b) AT-1: 14 treatment) then 10 days ambient (nominally 70° F., Example 5c) sand: 2 c) Sanded 40% RH) Second Topcoat: DHS CA8000 50103 blue (C thinner); cured at 120° F., 8-12% RH for 4-5 hours then 20-30 days ambient (nominally 70° F., 40% RH) 6 0.5% 10 nm aluminum DHS 70846 white (4:1 C:C2 thinner); 2 oxide cured at 120° F., 3% RH for 96 hours then 10 days ambient (nominally 70° F., 40% RH) Second Topcoat: DHS CA8000 50103 blue (C thinner); cured at 120° F., 8-12% RH for 4-5 hours then 20-30 days ambient (nominally 70° F., 40% RH) 7 0.1% 80 nm silicon oxide DHS 70846 white (4:1 C:C2 thinner); 4 cured at 120° F., 3% RH for 96 hours then 10 days ambient (nominally 70° F., 40% RH) Second Topcoat: DHS CA8000 50103 blue (C thinner); cured at 120° F., 8-12% RH for 4-5 hours then 20-30 days ambient (nominally 70° F., 40% RH) 8 0.1% 160 nm silicon DHS 70846 white (4:1 C:C2 thinner); 5 oxide cured at 120° F., 3% RH for 96 hours then 10 days ambient (nominally 70° F., 40% RH) Second Topcoat: DHS CA8000 50103 blue (C thinner); cured at 120° F., 8-12% RH for 4-5 hours then 20-30 days ambient (nominally 70° F., 40% RH) 9 0.1% 40 nm aluminum DHS 70846 white (4:1 C:C2 thinner); 4 oxide cured at 120° F., 3% RH for 96 hours then 10 days ambient (nominally 70° F., 40% RH) Second Topcoat: DHS CA8000 50103 blue (C thinner); cured at 120° F., 8-12% RH for 4-5 hours then 20-30 days ambient (nominally 70° F., 40% RH) 10 0.5% 40 nm aluminum DHS 70846 white (4:1 C:C2 thinner); 10  oxide cured at 120° F., 3% RH for 96 hours then 10 days ambient (nominally 70° F., 40% RH) Second Topcoat: DHS CA8000 50103 blue (C thinner); cured at 120° F., 8-12% RH for 4-5 hours then 20-30 days ambient (nominally 70° F., 40% RH) 11 0.1% <50 nm aluminum DHS 70846 white (4:1 C:C2 thinner); 8 oxide cured at 120° F., 3% RH for 96 hours then 10 days ambient (nominally 70° F., 40% RH) Second Topcoat: DHS CA8000 50103 blue (C thinner); cured at 120° F., 8-12% RH for 4-5 hours then 20-30 days ambient (nominally 70° F., 40% RH) 12 0.5% <50 nm aluminum DHS 70846 white (4:1 C:C2 thinner); 8 oxide cured at 120° F., 3% RH for 96 hours then 10 days ambient (nominally 70° F., 40% RH) Second Topcoat: DHS CA8000 50103 blue (C thinner); cured at 120° F., 8-12% RH for 4-5 hours then 20-30 days ambient (nominally 70° F., 40% RH) 13 0.5% 160 nm silicon DHS 70846 white (4:1 C:C2 thinner); 7 oxide cured at 120° F., 3% RH for 96 hours then 10 days ambient (nominally 70° F., 40% RH) Second Topcoat: DHS CA8000 50103 blue (C thinner); cured at 120° F., 8-12% RH for 4-5 hours then 20-30 days ambient (nominally 70° F., 40% RH) *Note: Per standard test protocol, the last 0.25 inch of each end of the foil is not used in the tear evaluation due to end effects and handling during test preparation.

Example 14

(46) Nanoparticle Effect on Color

(47) Delta E Comparison Between No Reactivator and Reactivator

(48) TABLE-US-00007 Color Shift (ΔE) Basecoat Color Activator White Red Blue AT-1 0.12 0.29 0.29 AT-1 w/0.5 wt % 20 nm silicon oxide 0.35 0.47 0.13 AT-1 w/0.5% wt % 10 nm aluminum oxide 0.32 0.21 0.20 AT-1 w/0.5% wt % 40 nm aluminum oxide 0.18 0.26 0.29

(49) Paint system: Aerodur 3001/3002 (polyurethane) basecoat-clearcoat system by AkzoNobel.

(50) AT-1 with or without nanoparticles is applied between basecoat and clearcoat No or only small shift in color with AT-1 No or only small additional color shift when nanoparticle is added at maximum concentration expected Concentration is by nanoparticle weight and not dispersion weight. Nanoparticles come in 20 to 50 wt % dispersions from manufacturer.

(51) This example demonstrates the treatment can be used with a colored basecoat and a subsequent clearcoat added on top without significantly shifting the color of the basecoat. This, of course, is not an issue if the top coat is also colored. For coatings requiring clear top coats, nanoparticles other than carbon black need to be used.

(52) It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art.

(53) In the claims which follow and in the preceding description of aspects, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various aspects of the present disclosure.

(54) It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the disclosure as shown in the specific aspects without departing from the spirit or scope of the present disclosure as broadly described. The present aspects are, therefore, to be considered in all respects as illustrative and not restrictive.