Attachment 2 Section2 5.pdf

5. CLEANING, PHOSPHATING, AND PAINTING OF AIR FLASK

Perform the following procedure for cleaning, phosphating, and painting the air flask:

Warning: The solvent used for vapor degreasing is 1.1.1 trichloroethane, which is a strong skin and eye irritant.

Also, vapor degreasing is performed at 165F and care should be exercised when handling hot parts.

1. Using standard procedures, vapor-degrease air flask to remove oils and greases.

2. Remove old and defective paint in a solution containing a heavy duty alkaline cleaner for ferrous substrates (Oakite Q9 or Equivalent); 32 – 48 ounces per gallon and 180 – 200F.

Parts must be water-rinsed and dried with pressurized air (30-psi maximum) before further processing.

3. Preheat air flask at 450 – 475F for 2 – 4 hours to remove contaminants from the metal.

4. Water-blast with warm water to remove contaminants from the metal. Allow the air flask to dry thoroughly.

Note: Before commencing sandblasting, install cap plugs to protect threads.

5. Sandblast all interior and exterior surfaces to remove rust, scale, paint residue, etc.

6. Remove blast residue with pressurized air (30-psi maximum).

Warning: The chemicals used in the phosphating process contain phosphoric acid, zinc phosphate, and chromic acid.

These are skin and eye irritants and are harmful if taken internally.

Caution: Phosphate solution should not be boiled or strongly agitated. This may cause sludge deposits on parts.

Caution: Bonderite 880 solution must be heated only while in use.

Caution: During phosphating, the air flask must be moved back and forth at frequent intervals to prevent the formation of air pockets.

7. Following the blast and without delay, remove cap plugs and transfer air flask to the zinc phosphate solution. Apply coating by employing the following operating parameters:

Solution: Light zinc phosphate (Bonderite 880 or equivalent)

Temperature: 180 – 200F

Time: 7 – 9 minutes.

Caution: Do not allow phosphate solution to dry on metal surface.

8. Spray cold water on air flask while withdrawing from phosphate tank. The water spray is necessary to rinse the phosphate solution from the surface and keep it from drying on the air flask.

9. Immediately rinse using acidified-rinse employing the following operating parameters:

Solution: Acidified rinse (Parcolene 95A or equivalent)

Solution concentration: One gallon acidified rinse (Parcolene 95A) per 100 gallons water

Temperature: 110 – 120F

Time: 30 – 60 seconds.

10. Dry with pressurized air (30-psi maximum).

11. Inspect the air flask to ensure that the inorganic coating is evenly deposited with a uniform crystalline texture and a pattern not readily visible to the unaided eye. The coating shall show no evidence of etching or intergranular attack of the base metal and shall be dark gray or black in color. The coating shall be free of white stains (due to dried phosphating solution), rust, and fingerprints. Non-uniformity of color due to heat treatment, degree of cold work, composition of the basis metal, or discoloration from acidified rinse shall not be cause for rejection.

12. Store air flask in cardboard box or wrap in paper to protect from shop soils, dust, and moisture.

Warning: The phenolic resin coating may be toxic and a skin irritant. Work shall be performed in an area with ventilation adequate to maintain airborne pollutants below

NAVOSH-permissible exposure levels.

Note: Air flasks transported outdoors during inclement weather (rain, snow, etc.) shall be covered with a sheet of dry plastic. Tarpaulins are not fully waterproof and do not afford the required protection.

13. Paint all interior and exterior surfaces of the air flask, except the counterbores, countersinks, and threads in the openings in each end, with Heresite P-413 in accordance with the following procedure:

a. Thoroughly stir container of Heresite P-413 to a homogeneous mixture. Use a shaker or power-stir equipment.

b. Measure Heresite P-413 by volume into a suitable, clean container.

Warning: Denatured alcohol is highly flammable as well as an eye irritant. Use it carefully and only as described.

Note: The total dry film thickness of the Heresite coating for interior and exterior surfaces shall be 0.0015-inch minimum.

c. Thin the Heresite P-413 with denatured alcohol to a viscosity of 18 – 20 seconds using a No. 2 Zahn Cup. The alcohol should be added slowly while continuously stirring the mixture. The approximate thinning ratio is one part Heresite P-413 and one part denatured alcohol.

d. Stir the thinned phenolic coating and strain into the paint container using organdy or comparable strainer material.

Note: The air flask may be preheated to 120F (maximum) before painting to permit faster solvent evaporation.

e. Insert a rod or long wire through the center of the flask for support and hanging.

f. Apply Heresite P-413 to interior curve surfaces using a DeVilbiss MBC-510 tank gun with an MBX 4201 extension or equivalent. Adjust air pressure to 40 ± 5 psi. Insert the gun all the way into one end and withdraw while applying a uniform coating on all surfaces. Allow the Heresite film to dry for approximately 10 minutes. Insert the gun all the way into the hole at the opposite end and withdraw while applying a uniform coating.

g. Apply Heresite P-413 to interior end (boss) surfaces using a DeVilbiss JGA-502 suction spray gun or equivalent. Adjust air pressure to 40 ± 5 psi. Insert gun into holes on each end of the air flask to apply a coating on the opposite end (boss) surfaces.

h. Apply Heresite P-413 to the exterior surface using a DeVilbiss JGA-502 suction-type air gun or equivalent. Adjust air pressure to 40 ± 5 psi. Apply two wet coats to obtain a coating thickness of 0.0015-inch minimum, allowing approximately 10 minutes of air drying between coats.

i. Air-dry for 30 minutes (minimum) to allow solvents to vaporize before baking.

j. Transfer the air flask to an oven and pre-bake the coating for 15 minutes at

150 – 200F.

k. Remove the air flask from the oven and allow to cool to room temperature.

l. Transfer the air flask to an oven for final baking at 400 ± 15F for 1 hour. Before final baking, the color of the Heresite coating is light tan. After final baking, the color is chocolate brown. An alternate cure cycle is 350F for 3 hours, but the final baking temperature must NOT be lower than 350F.

Warning: MEK is highly flammable as well as an eye irritant. Use it carefully and only as described.

m. Perform a solvent resistance test if there is doubt as to whether the coating is fully cured. Saturate a lint-free cloth with MEK and wipe a coated surface. The MEK will not soften or remove any of the Heresite if the coating if fully cured. If any coating is removed, parts of that lot shall be rebaked to ensure that a full cure is obtained.

n. Perform a visual inspection to ensure that there is no evidence of runs, sags, blisters, “orange peel,” specks, bumps, or roughness.

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o. Perform an adhesion test by pressing a 6-inch strip of pressure-sensitive tape

(No. 250 manufactured by Minnesota Mining and Manufacturing Company) in firm contact with the painted surface. Wait approximately 10 sec. Grasp the free end of the tape and rapidly strip it from the painted surface by pulling back at approximately a 180 angle. The tape shall show no evidence of removal or loosening of the paint when tested at any time after the coating has been properly cured and air-cooled to room temperature.

p. Perform a hydrostatic test on the air flask for 3 minutes at 4500 psi. Inspect the paint after the test for defects.

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