(e)
Large quantities of methyl ethyl ketone peroxide resulting from breakage of spillage should be absorbed in Pearlite or Vermiculite.
(f)
Cleanup of equipment
1) Prior to expiration of the pot life, thoroughly clean the spray gun with acetone or methylene chloride.
502
Feb 20/94 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 53-52-0 Page 701
(2)
Equipment and Materials
(a)
Erosion Coating - Prestec Enamel - No. 2381 (Ref 20-30-41)
(b)
Siphon Spray Gun - DeVilbiss JGA-502, No. 30 cap, No. AV-15-EX tip, or equivalent
(c)
Mixing Cup - No. 2 Zahn
(d)
Initiator - MIL-M-81351 (MEK peroxide) (Ref 20-30-31)
(e)
Solvent, Methylene Chloride - MIL-D-6998 (Ref 20-30-31)
(f)
Solvent - Acetone - 0-A51 (Ref 20-30-31)
(g)
Solvent - Aliphatic Naphtha - TT-N-95 (Ref 20-30-31)
(h)
Abrasive paper
(i)
Cheesecloth
(3)
Prepare for Painting
(a)
Prestec enamel consists of base component only with catalyst and thinner to be supplied separately.
(b)
Agitate Prestec base thoroughly just before mixing.
(c)
Measure required amount of Prestec base into cup of a siphon spray gun.
(d)
Thin base for 25 to 35 seconds in a mixing cup with methylene chloride.
(e)
When ready to begin spraying, slowly add 2.0 +0 .5% by volume methyl ethyl ketone (MEK) peroxide to thinned base while stirring base. Do not add base to catalyst. Stir catalyzed material for 1 to 2 minutes to ensure a homogeneous mixture.
WARNING: MEK PEROXIDE IS AN OXIDIZER. AVOID BREATHING VAPOR. DO NOT GET IN EYES, ON SKIN, OR ON CLOTHING. KEEP AWAY FROM HEAT, SPARKS, AND OPEN FLAMES. DO NOT ALLOW CONTACT WITH COMBUSTIBLES.
53-52-0 Nov 15/80
Page 702
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
(f)
Record the time of adding the catalyst to the Prestec base and the temperature of the paint facility. The material should be used and the spray gun emptied and flushed prior to expiration of the pot life. Pot life at various temperatures is listed below:
Temperature Pot Life (Minutes) 62° 57 67° 40 72° 30 77° 20 82° 15 87° 11
(g)
All loose and damaged paint shall be removed by sanding with 280 grit or finer abrasive paper or Scotch-Brite pads. Do not expose fiber reinforcement.
(h)
All areas of bare fiberglass shall be sanded with 280 grit or finer abrasive paper or Scotch-Brite pads to remove gloss. Feather all paint edges using 280 grit or finer abrasive paper. Do not abrade the glass fiber reinforcement.
(i)
Remove sanding dust by cleaning, using naphtha followed immediately by wiping with a dry, clean cheesecloth. Repeat until all sanding residue has been removed.
(j)
If any pinholes exist, fill per Chapter 51, Prepaint Cleaning and Pretreatment. Do not allow solvents to contact the applied static conditioner as they will remove it from pinholes.
(k)
As soon as possible apply Prestec enamel so as to blend in with the surrounding surfaces. If further blending is required allow the enamel to cure approximately 3 hours then blend in using 280 grit or finer abrasive paper with aliphatic naphtha or water.
NOTE: If balling up on the paper occurs, the paint film is not sufficiently cured and additional curing time must be allowed.
(4)
Paint Nose Radome
(a)
For application use a DeVilbiss JGA-502 siphon spray gun, No. 30 cap and No. AV-15-EX tip or equivalent.
(b)
Use 35 to 40 pounds per square inch air pressure at the gun.
(c)
Apply one light cross-coat of Prestec to radome surface. After 10 minutes or one-half of pot life has expired (whichever is less), apply a second wet cross-coat of Prestec to obtain a total dry film thickness of 2.5 +0.5 mils.
(d)
In areas where one enamel color overlaps another, total dry enamel thickness shall not exceed 5 mils.
(e)
Allow coating to dry 24 hours or more at 70°F or higher before exposing coating to rain or outdoor temperatures below 70°F.
(f)
Dry-to-tape time is 6 hours at 70°F. This drying time is dependent on temperature and humidity and is given here as a guide only. This time may be varied providing tape after removal has had no visible effects on enamel film. Exact time can best be determined on practice panels under shop conditions identical to those under which radome is painted.
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