Tech_Data.pdf

T.O. 1·1-24

4.40.2 Application Technique (Brushing or Spraying)

and Coating Thickness.

11 WARNING II

Spray polyurethane in a paint booth designed for spray painting, or in a well-ventilated area.

Bureau of MineslNationa! Institute for Occupa tional Safety and Health approved organic res pirators with a fiberglass prefilter may also be required. Brushing areas that cannot be readily ventilated may also require respiratory protec tion. The Base Bioenviron1nental Engineer must be contacted to evaluate ventilation and respiratory protection.

The techniques of paragraph 4.39.1 through paragraph

4.39.5 are applicable to polyurethane coating manufactured to Specification AMS SAE-C-83445. Son1e manufacturers may require that a non-yellowing white topcoat be applied over the polyurethane vehicle. 1'he thickness of this coat shall be 0.002 to 0.003 inches thick (overall thickness of the coating and primer 0.014 ±0.002 inches).

4.41 APPLICATION OF AMS 3138A, PRIMER

AND COATING, FLUOROCARBON ELASTOMERIC.

a. After preparation of the surface, apply 0.001 to

0.002 inch thickness of Chemglaze 9224 wash primer provided in kit using enclosed instructions.

b. After one hour dry time, overcoat primed surface with the activated and thinned B-274 basecoat (per enclosed instruction) to required coating thickness allowing only sufficient tin1e between coats for solvent evaporation.

c. After 10 to 30 minutes, activate and apply one crosscoat or two standard coats of white Type II fluoroelastomer tiecoat.

d. Allow 45 to 60 minutes dry time before applying the activated Type V anti-static topcoat in suffi cient quantity to provide co1nplete hiding of the tiecoat. ('fwo applications are usually sufficient to provide both color and anti-static properties.)

4.42 PATCHING OR RETOUCHING DAMAGED

COATINGS.

NOTE

If the coating age exceeds more than one year, the old coating cannot be reactivated suffi ciently to permit a good bond between the new and old coatingi;. Therefore, such patches will be of a ~ temporary nature.

a. Sand the da1naged surface to a feather edge. The sanded surface should extend beyond the damaged area approximately one inch. Clean the sanded surface with a clean lint free cloth dampened with SkyKieen 1000 and allow to dry thoroughly. Apply primer and coating(s) as previously directed herein.

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Exercise extre1ne caution to prevent uneven and excessive build-up of coating when making repairs to radome coatings. Excessive coating thickness wiU reduce the electrical transmission efficiency of the radome, and in the case of dopp!er and fire control radomes could result in beam detlection errors beyond tolerable limits.

4.43 REMOVAL OF COATINGS.

4.44 REMOVAL OF SAE AMS-C-83231 AND SAE

AMS-C-83445 POLYURETHANE COATINGS AND

AMS3138A FLUOROCARBON ELASTOMERIC

COATINGS.

There are two 1nethods of ren1oval of organic finishing systems; chemical and n1echanical. Each method has its own set of procedures, precautions, restrictions, and lin1ita tions and therefore, each will be explained separately.

NOTE

User must gain specific System Program Office (SPO) or Equipment Item Manager approval for use of the coating removal materials and processes contained in this technical order.

4.44.1 Chemical Removers.

11 WARNING 11

Handling and use of coating removal solvents requires precautions commensurate with their toxicity and flashpoint characteristics. Chen1i cal removers are toxic to skin, eyes, and respir atory tract. Contact Bioenvironmental Engi neering for detemlination of need for and selection of proper personal protective protection.

4.44.1.1 Radon1es will be inspected for damages that

penetrate the face plies prior to application of any chemical coating removal agents. 1'o prevent the solvent from enter ing the radome core, dan1ages that penetrate the face plies will be covered with tape, Stock No. 7510-00-684-8803 or equivalent. The tape should extend approximately three inches beyond the edges of the dmnaged area. Do not attempt to remove the coating under the tape; this coating win be removed with the face ply when the damaged areas are repaired by hand sanding.

4.44.1.2 There are no USAF-approved specification

removers for these finish systems, however Methyl-ethyl ketone, TT-M-261, and specific benzyl alcohol/hydrogen peroxide based proprietary coating removers have been tested and found to be effective for removing radome coatings. The following benzyl/hydrogen peroxide alcohol re1novers are currently authorized for use on radon1es:

PIN Manufacturer 9095 B&B Tritcch

875 W. 20th St.

1124727568C Highlight

PIN

AS 5050

Desolift 5269

E-2787

Manufacturer Hialeah, FL 33010-2310 Aero Solutions

8323 Woodcliff Blvd Sehna, TX 78154

PPG Aerospace PRC-DeSoto 12780 San Fernando Rd.

Sylmar, CA 91342

Cee-Bee™ Div., McGean-Rocho, Inc.

!314 Murphy Ave.

Atlanta, GA 303 l 0-4004

4.44.1.3 Chen1ical ren1oval of radome coatings shall be

accomplished by one of the following methods:

a. Using Methyl-ethyl-ketone (MEK), IT-M-261.

Thoroughly saturate the surface of the rado1ne using a continual stream of MEK. Perfonn the removal process by placing the radome over a locally constructed drip pan so that the solvent drain off may be caught and reapplied to the radome coating. The drip pan should have a drain outlet and a means of positioning the radon1e so that the radon1e base will not be submerged in the solvent accumulated in the drip pan. Alternatively, the radome n1ay be covered with absorbent, non synthetic cloth saturated with MEK. The cloth 1nay be covered with a suitable vapor-resistant material to prevent rapid solvent evaporation. Once the solvent has caused the coating to blister and soften, scrape the coatings from the radome surface using weapon system engineer approved non-metallic scrapers, taking care not to damage the fiberglass epoxy skin. Maintain saturation of the radome surface throughout the scraping process. Any residual coatings should be removed by hand sand ing with 280 grit or finer abrasive paper taking care not to damage the radome surface.

T.O. 1·1·24

I CAUTION I

• Prolonged exposure of composite radome substrates to solvents may cause deteriora tion of the resins, therefore the surface should only ren1ain wetted with MEK until the coating is sufficiently loosened to allow removal with non-metallic hand scrapers.

• When using non-metallic hand scrapers to strip the erosion coating, care must be exer cised to prevent damaging the radome surface.

NOTE

Direct sunlight, ten1peratures greater than 85°F, and/or low humidity, (less than 40 percent) can cause rapid evaporation of the solvent and prevent proper stripping of the radome.

b. Using above listed benzyl alcohol-based coating removal con1pound<;. Thoroughly apply the benzyl alcohol coating removers to the surface of the radome with brush, roller, or spray (preferable) and allow dwelling until the coating is completely lifted from the substrate. Periodic agitation of the surface with non-metallic brushes has been shown to improve stripper effectiveness on some coatings.

Once the solvent has caused the coating to blister and soften, scrape the coatings fron1 the radome surface using weapon system engineer approved non-n1etallic scrapers, taking care not to damage the fiberglass epoxy skin. A final rinse with mediun1 pressure hot water should be used to remove the remaining coating remover and loose coatings. Any residual coatings should be ren1oved by hand sanding with 280 grit or finer abrasive paper taking care not to damage the radome surface.

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1124727568C Highlight