Repainting of Aircraft and Components

1. PURPOSE
The purpose of this process specification is to provide a standard procedure for the repainting of aircraft and components.

2. SCOPE
This specification describes the requirements and procedures for the repainting of aircraft exterior, interior and components including cowlings, thrust reversers, wheels and brakes etc. The processes apply to primarily for aircraft with notes added for components where necessary.

3. SPECIFICATION REFERENCES
a. CAA CAIP Part 2 Leaflet 2-7.
b. FAA AC65-15A Chapter 4
c. Airworthiness Notice No. 82.
d. Applicable Boeing Material Specifications.
e. Paint manufacturers’ Instructions, Processes and Standards
f. Component CMM/OHM.
g. Applicable aircraft exterior markings and colour scheme drawings.

4. MATERIAL REFERENCES
Paints and chemicals listed in Appendix A are for reference; and are not exhaustive. Equivalent products may be used based on the specifications where stated since there are many such products in the market. Obtain the product technical data sheet for guidance prior to using it. Consult Technical Services as needed.

5. SAFETY PRECAUTIONS

a) Carry out all work in adequately ventilated area.

b) Spray paint personnel MUST wear suitable respirators containing filter cartridges for organic vapours when applying epoxy and polyurethane finishes to prevent inhaling spray vapours. Wear rubber gloves, hoods and coveralls so that these materials do not come in contact with exposed skin

c) Where air circulation is insufficient, an air-supplied respirator is required.

d) Observe manufacturer’s safety instructions and precautions at all times.
Avoid prolonged or repeated contact of solvents or conversion coating material with skin. Use gloves, goggles and overalls to prevent contact with stripping material solvents or conversion coating materials.
Note: Do not allow paint stripper to contact skin.

e) Wash body skin or clothing with copious amount of water immediately after contact with any solvent, paint stripper or conversion coating material.

f) Should liquid curing solution or chemicals contacts the skin or eyes, wash skin with soap and water; flush eyes with large amounts of water and seek medical attention immediately.

g) Polyurethane and epoxy coatings are flammable materials, observe fire safety precautions at all times.

h) Ensure aircraft being painted is electrically grounded.

6. GENERAL NOTES

a) Water-Break-Free.
A water-break-free surface is one which maintain a continuous water film for a period of at least 30 seconds after having been sprayed or immersion rinsed in clean water at a temperature below 100ºF (38ºC).

b) A properly cleaned surface is essential to achieve a paint system of a high quality and a long lifetime. When a surface is not cleaned well, problems can occur, include adhesion problems, blisters and pinholes.
– Use clean lint-free cleaning cloths.
– Clean the surface using the “wipe-on-wipe-off” method (use two cloths, one soaked in cleaner to wipe on and the other, a clean, dry cloth to wipe off immediately)
– Do not let the cleaner dry on the substrate.
– Do not touch the degreased surfaces prior to painting (clean the aircraft as the last activity, after masking).
– Thoroughly check the surface for any faults after degreasing.
– Final clean just before painting.

c) Paintshop foreman is to ensure that painting task carried out is adequately defined by technical documents, drawings, data sheets, etc including PS003. Contact Technical Services if information is insufficient.

d) Painter shop foreman is to notify Planning and Maintenance of repainting schedules to plan any structural inspections scheduled including non-destructive inspections that could be better accomplished following paint removal.

e) All painted surface are to be tested/inspected as per para 18.
f) Any stencils/decals can be applied on painted surface after paint adhesion satisfies tape test per para 18.

6.1 PAINT STORAGE AND HANDLING

a) Paints should be mixed, thinned and applied as required in accordance with manufacturers’ data sheets. Do not exceed dry film thickness recommended for best results.

b) Stirring of paints
Where a skin has formed in the paint, it should be removed before stirring. A flat-bladed non-ferrous stirrer should be used.

c) Mixing of paints
Before mixing, check to confirm the right products (base, hardener, and thinner) and that there is enough of each product available to complete the painting procedure. Check data sheet for the correct amount of hardener and thinner to be used.

d) Thinning of paints
The necessary degree of thinning depends on the type of spray equipment
– air pressure
– atmospheric conditions
– kind of paint

The viscosity range or thinning ratio is indicated on the data sheet of each product. Accurate thinning is important for optimum viscosity for best results. Use the correct viscosity cup to check the viscosity as needed.
Note; for tropical conditions, adjust to lower end of viscosity.

e) Straining of paints
All materials should be strained before use. Metal gauze (60 mesh) muslin or three layers of cheese cloth are suitable strainers.

f) Paint must be stored under the right conditions to guarantee the quality. Store the paint in the original unopened containers at a temperature between 5C and 25C. Before using the paint, it must be at the same temperature as the ambient.

g) Paint should be stirred, thinned and strained just before use. The lids of all containers should be wiped clean before opening. Containers should not be left open longer than absolutely necessary, otherwise excessive solvent losses will occur and hardeners may be affected by moisture.

6.2 MASKING FOR PAINTING

a) Masking is to protect various areas from chemicals e.g. stripper and paint including over-spray. Adequate masking is a must around all openings that could admit paints and chemicals e.g. doors, seams, wheel wells.

b) Use aluminium tape to protect specific areas and seams from paint-stripper.

c) Use masking tape to mask paper (tape is not waterproof).

d) Use cello-tape to line out cheat lines and decorative lines.

e) Use kraft paper to protect large areas from over-spray during painting.

f) Use plastic coated paper or impregnated paper to protect from water and chemicals.

g) Use plastic sheet during stripping and spraying in order to mask bulk areas to avoid overspray but ensure that freshly painted surfaces are fully cured before draping with plastic (polythene). This is to avoid locking in of solvent vapour.

Note: Do not use plastic sheets along the border of area to be painted. This is to avoid dust in the wet paint caused by electrostatic charge of plastic sheets.

6.3 EQUIPMENT CLEANLINESS
Keep the application and mixing equipment clean with solvent cleaner e.g C28/15 to avoid clogging of spray nozzle and depositing of foreign material on the coating surface.

If possible, air used for spray gun operation should be from a separate supply. If taken from a general supply line, install sufficient regulators and manifold to buffer abrupt changes or surges in the air pressure. Install sufficient oil and moisture separators in the air system and blow down the air hose at least twice daily (when in use).

7. FLIGHT CONTROL REPAINTING

a) If any flight control surface requires repainting LAE should determine if balancing is involved prior to painting. Such surfaces should be removed from the aircraft to allow re-balancing unless SRM permits re-balancing through calculation.

b) Typically flight control surfaces should be stripped of paint chemically (unless fiberglass/graphite/kevlar composite is involved) or mechanically. LAE is to ensure flight control surface is rebalanced per SRM requirement prior to reinstallation per applicable MM after repainting.

c) LAE is to note down the balancing data prior to repainting.

d) LAE is to coordinate with Technical Services to determine the basic weight and corresponding center of gravity position for flight controls as needed. See also Para 19

e) Fibreglass and graphite/kevlar composite surfaces are to be sanded down using grit 400 or finer abrasive paper or very fine Scotch Brite Pads to remove paint coating.

Note: Do not use paint stripper on fiberglass/graphite/kevlar surface or fiberglass repair patches on aluminum skinned composites

8. SURFACE INSPECTION PRIOR TO PREPARATION
This paragraph applies also to repainting of aircraft components.

a. Ensure aircraft is located in a hangar that is relatively dust free. Electrically ground aircraft per applicable Maintenance Manual.

b. For components, ensure that parts are in relatively dust free area.

c. Spot check the adhesion of the paint as necessary with pressure sensitive adhesive tape 3M 600 or equivalent as per para 18. If the paint comes away with the tape, paint removal is recommended – proceed with para 10 or 13 as applicable. Otherwise go to para 9.
Note: Check at sufficient locations to confirm satisfactory adhesion.

d. Use appropriate tools to remove existing sealant and decals on the surface to avoid scribe marks/lines, particularly on aircraft fuselage lap and circumferential joints. Putty knives, razor blades or any sharp tools are prohibited to be used for sealant and decal removal. Refer to SB 737-53A1262 and AWC ref AWC/Boeing737/001(03) dated 6th May 2003

9. WHEN EXISTING PAINT DOES NOT REQUIRE STRIPPING.

a. Remove any chipped paint around joints and fastener heads. Use aluminum oxide paper grade 280 or finer to feather edges.
Smooth out areas of built-up paint using aluminum oxide paper grade 280 or finer.
Note: Ensure all traces of cleaner are removed by flooding with water and scrubbing with Scotch Brite Pad.

b. Continue scrubbing until a water-break-free surface is attained.

Note:

a) When oil stains or other contaminants cannot be removed by the above means, use a clean cloth moistened with MEK or equivalent to wipe affected surface. Wipe area dry immediately with dry clean cloth.

b) Do not apply excessive amount of MEK which will soften the paint film. If a clean water break free surface cannot be obtained, the paint must be stripped as per para 10 or 13.

c. Allow treated area to dry for about two hours. Ensure no water is trapped at joints, seams, opening etc.

d. Mask as required using masking tape and kraft paper or plastic sheet.
Note: Where masking tape was used on areas to be subsequently painted, ensure all traces of tape adhesive are removed. A clean cloth moistened with MEK may be used. Do not allow any MEK to remain on the surface. Immediately wipe off with clean dry cloth.

e. Proceed to Para 14.

10. WHEN EXISTING PAINT REQUIRES TO BE STRIPPED.

Note: Do not use paint stripper to remove paint on composite materials, fiberglass panels and fiberglass repair patches on aluminum skinned composites.
Use only Environmentally Friendly (EA) paint strippers that do not contain phenolics so as to allow easy disposal.

10.1 MASK FOLLOWING CRITICAL AREAS USING ALUMINIZED PAPER.
For aircraft this must be carried out meticulously to avoid stripper affecting certain material adversely; and stripper getting into crevices and gaps. For components mask areas that are not to be paint-stripped or where it is not desirable for strippers to be trapped.

a. Cabin and Cockpit Windows including window on Doors
Refer to para 10.2.

b Radome & De-icing Boot
Cover all exposed areas if radome and deicer boots if any are removed.

c Door and Openings
Cover all doors gaps and openings with tapes.

Vertical Fin
Cover exposed areas if rudder is removed. Cover fiberglass/composite panels and access openings.

d Wing & Horizontal Stabilizers
Cover wing-to-fuselage fairings and/or areas covered by these fairings; or cover areas exposed if such fairings are removed. Cover also between fuselage and horizontal stabilizer and fuselage-to-horizontal stabilizer attachment areas.

e Fuselage
Mask all cavities, sealed joints and static and pitot points.

f Landing Gear
Mask landing gear with aluminized kraft paper or plastic sheet and tape.

g Ground Support Equipment
Mask all ground support equipment in close proximity and likely to be affected by paint stripper with double layer aluminized paper and tape.

h Plastic or Fibreglass Structures (Including Composite Material)
Cover these surfaces if not removed from aircraft.

10.2 MASKING OF COCKPIT, CABIN AND DOORS’ WINDOWS.
Majority of these windows are made from perspex and will be adversely affected by chemical stripper. Proper masking is therefore critical.

a. Cover all windows surface with aluminized kraft paper or plastic sheet and aluminum tape around the window gaps between fuselage skin and window frame with aluminum tape.

Note: Ensure aluminized kraft paper or plastic sheet is firmly pressed onto the base material by rubbing firmly with a rubber roller over the tape.

b. Cover window with a second layer of larger aluminized kraft paper or plastic sheet and aluminum tape. Ensure that the aluminized kraft paper or plastic sheet overlap is at least 1” over the first layer of aluminum tape before the second layer aluminum tape is applied.

c. Apply third protective screen over all passenger and cockpit windows using curtain of aluminized kraft paper or plastic sheet. This third protective screen is to span lengthwise the fuselage. Overlap where applicable.

Note: Ensure aluminized kraft paper or plastic sheet covers at least two inches above and below the windows.

10.3 PAINT STRIPPING PROCEDURE

a. Preparation
Washing is generally not required except for oily or greasy areas; but it is recommended so that all oils are removed to hasten the action of stripper.
Surfaces to be stripped must be dry and the temperature should be between 15 and 35C. Stripping should not be done in hot sun or rain.
The stripper should be thoroughly mixed in its container before use and it is advisable to keep the container closed when not in use. Keep paint strippers away from heat and sun and take care when opening a container (pressure).

b. Equipment for stripping aircraft
Pump: Use a standard 5:1 or 10:1 stainless steel barrel pump with teflon packing.
Use a stainless steel/teflon hose, fitted with a spray gun and swivel, stainless steel spray wand, and a non atomizing tip.
Test assembled equipment to ensure good working order, with no leaks.
Bristle brushes, squeegees, Scotch-Bright pads etc., normally used in stripping operations can be used with paint strippers.

c. Equipment for stripping components
same as (b) above except the pump.

10.4 PAINT STRIPPER APPLICATION

a. Apply a full coat of paint stripper to the surface to be stripped, working from the bottom up and front to back for the fuselage.
If slippage occurs: apply a mist coat of paint stripper to the surface experiencing adhesion problems, let stand 10-15 minutes and re-apply a full coat.

b. Effect of temperature:
EA Paint Strippers are sensitive to temperature. For best results, the ambient temperature, the surface temperature of the aircraft, must be above 20° C, ideally 30° C rises in temperature are preferred. A 10° C rise in temperature will usually halve the stripping time.

c. Dwell time:
Depending on the stripper being used, paint system, film thickness, age of paint system, original surface treatment, temperature; recommended dwell time will vary from one to four hours. Do not agitate the stripper during dwelling. Do not allow the stripper to dry on the surface. Usually the paint will blister when loosened. Some paints do not blister and should be tested for looseness by scraping very gently with wooden or plastic scrapers. The stripper should be removed from the aircraft when it appears to dry or beads of water appear on the surface in large numbers.

Note:
a) Complete stripping of primer is not required provided remaining primer adhesion to metal can withstand scratching or pass the adhesion test per Para. 18.

b) If primer removal is required or if primer sticks stubbornly re-apply stripper and agitate such areas with white Scotch Brite Pads.

c) Never use steel wool or a steel brush or steel scrapers as tiny bits of steel will become embedded in the aluminium and this leads to corrosion.

d. Remove as much as possible stripper and loose paint residue using non-metallic scrappers and rags. Thoroughly rinse the reworked area with pressurized water hose and scrub. Use nylon brushes with white Scotch Brite Pads to remove residue.

e. For components, spray application may not be necessary but can also be used. Brush application of stripper can be used as alternative.

10.5 AGITATION AND REMOVAL OF LOOSE PAINT

a. Agitate a workable area with a stiff polypropylene brush.
b. Squeegee off all loosened paint.
c. If stripping is not complete, re-apply stripper as necessary per para.

10.4.
d. Hand work with Scotch Brite Pads to remove any residue.
Note: TURCO5948-DPM Cleaner can be used to help lubricate the surface for the Scotch Brite Pads.

10.6 WASH DOWN

a. To remove any remaining paint and/or paint stripper residues, thoroughly wash the entire aircraft or components with a 25% (vol) solution of TURCO 5948-DPM or equivalent, bottom to top, front to back for fuselage.

b. Rinse thoroughly with water, bottom to top and top to bottom, front to back.

c. Inspect bare surfaces for corrosion and other defects.

Note: for components, usually the entire components can be spray rinsed at one go.

11. SURFACE ETCHING/BRIGHTENING

11.1 WASHING PRIOR TO ETCHING (ALKALINE CLEAN)
a. Chemicals
Prepare the TURCO 5948-DPM solution by mixing 1 part TURCO 5948-DPM with 3 parts potable water (a 25% by volume solution)

b. Equipment
Same as 10.3 b

11.2 ALKALINE CLEANING PROCEDURES

a. Apply the TURCO 5948-DPM solution from the keel of the aircraft upward to the top of the aircraft in approximately 20 feet long sections. The length of the section should be expanded or shortened based on manpower and equipment available.

b. After the TURCO 5948-DPM is allowed to dwell for a few minutes, use Scotch Brite Pads to thoroughly agitate, bottom to top, front to back for the fuselage, making sure that the entire surface is completely scrubbed.

c. As one section is being agitated, the TURCO 5948-DPM solution should be applied to the next section.

d. Once a section has been agitated, it should be thoroughly rinsed with high pressure, high volume water (warm is better than cold). The rinsing should begin at the bottom of the aircraft section and work up to the top, then back down again, repeating this sequence until all cleaner is rinsed from the surface. Pay particular attention to seams, door opening, etc., that could trap stripper residue.

e. While one section is being rinsed, the next section should be agitated.

f. This process should continue until the entire aircraft fuselage has been thoroughly cleaned and is water break-free.

Note: For components, spray application as above is usually not necessary. Brush apply TURCO 5948-DPM, agitate with white scotchbrite pads as necessary followed by thorough rinsing with water.

11.3 ETCHING PRIOR TO CONVERSION COATING
This step is optional, and may be omitted for aircraft. It is not necessary for components.

a. Chemicals
Prepare the TURCO METAL-GLO #6 solution by mixing 1 part TURCO METAL GLO #6 with up to 1 part potable water (a 50% by volume solution)

CAUTION:
All High strength steel parts or fittings should be masked off with polyethylene sheeting or other water and acid resistant material using water proof tape.

b. Equipment
Same as 10.3 b

11.4 ETCHING POCEDURE

a. To help eliminate any tendency to splotch the surface, wet the aircraft surface with water prior to the application of the TURCO METAL GLO #6 etchant. Apply the TURCO METAL GLO #6 solution from the keel line upward to the top of the aircraft in approximately 20 feet long sections. The length of the section should be expanded or compressed depending on manpower and equipment available.

b. After the TURCO METAL GLO #6 has been allowed to dwell for 10-20 minutes, using Scotch Brite Pads, thoroughly agitate, bottom to top, front to back for fuselage, making sure the entire surface is completely scrubbed.

c. As a section has being scrubbed, the TURCO METAL GLO #6 solution should be applied to the next section.

d. Once the first section is agitated, it should be thoroughly rinsed with high pressure, high volume water (warm is better than cold). The rinsing should begin at the bottom of the aircraft section and work up to the top, then down again. Continue this rinsing pattern until the water sheets from the aircraft in a smooth, bubble free film. Pay particular attention to seams, door openings, etc., that could trap etchant residue. It is extremely important to follow this rinsing procedure – bottom to top – to avoid streaking the aircraft.

e. While one section is being rinsed, the next section should be agitated.

f. This procedure should continue in a smoothly flowing operation until the entire aircraft has been thoroughly etched and the aircraft has been thoroughly etched and the aircraft surface is completely water break-free.

11.5 INSPECTION
LAE is to inspect for corrosion and for damaged sealant. Replace sealant as required. Inspect lap joints for scribe line damage per relevant documents.
Note: Inform Technical Services of any major corrosion findings.

11.6 CLEANING BARE ALUMINUM SURFACES
Clean bare aluminum surface with 1:1 MEK/toluene mixture or equivalent, and check for water break-free. It may also be carried out for painted surfaces that have been rubbed down as necessary.

12. CONVERSION COATING (CHROMATE) APPLICATION

a) Apply chromate conversion coating Alodine 1200 or 1000 per SRM/MM 51 instructions to produce a coating that meets SRM/MM requirements.

b) Ensure water break free surface during rinsing after the alodine treatment.

c) Allow aircraft/component surface to dry. Wipe and blow seams/lap joints dry to help minimize entrapment of moisture and other contaminants in seams and lap joints.

d) Wipe all surfaces with Cleaner C28/15 or other approved solvent cleaner and clean with two rags, one wet/one dry (“wipe on/wipe off” method). Change often to avoid contamination.

e) Tack with tack cloth before primer application. It is now ready for primer application.

f) Remove all contaminated masking from the aircraft and clean the surrounding environment.

Note: The degreased surface should not be touched with bare hands (wear gloves) and should be protected from any contamination before paint application.
If surface has been allowed to collect dust or other contaminants, wipe with MEK or toluene or other suitable cleaning solvent using low lint cloth or rumple cloth.

g) If the time between cleaning and primer application exceeds 12 hours, solvent clean the aircraft/component surface using a blend of MEK and Toluene or other suitable cleaning solvent. Use clean low lint cotton cloth. Cloth should not be dipped into solvent cans as this will contaminate the clean solvent.
Either pour solvent onto the rag or, using an atomizing spray bottle, spray solvent directly onto the surface and wipe dry. Change cloth frequently.

13. PREPARATION OF PREVIOUSLY PAINTED SURFACES (NOT CHEMICALLY STRIPPED)

a) Wash surface with an alkaline cleaner mixed as specified by the manufacturer.

b) Sand (rub down) painted surface per 13.1.

c) Sand areas that cannot be chemically stripped (i.e. composite areas); and also during paint rework (i.e. removing runs, orange peel, dust etc) or when the maximum re-coatable time has elapsed.

Note: Before sanding, the surface must be free of grease and other contaminants to avoid grease being sanded into the surface, which will cause bonding problems.

13.1 SANDING (rub down) APPLICATION

a. Always wear mask, gloves and goggles during sanding.

b. Electrically ground the surface before sanding to avoid frictional (static) electricity.

c. Use the right type of sandpaper for every paint system. The product to be applied determines the sanding grades to be used.

d. Decide on the successive sanding steps for each paint system remembering not to jump any more than 100 points finer at any time. i.e. from P.180 the finest you could go would be P.280 if you wanted to finish with P. 320. This is to avoid sanding marks in the topcoat.

e. When sanding with a sanding machine, avoid mushroom head rivets, seams and tapes or decals. These areas must be treated by hand, preferably using a Scotch Brite pad Type A (or very fine).

f. When sanding old paint systems, sand to the primer to avoid a building-up of too many layers. Too thick paint systems tend to lose their elasticity after a while, which lead to cracking and peeling-off.

g. With wet sanding (optional) the area has to be kept wet with water and sponge. Change the sanding water regularly. After wet sanding rinse the area thoroughly with clean water and dry off.

a. After wet sanding, ensure the surface is dry before painting. Wait at least 14 hours and use compressed air to remove water from seams and rivets (remove dirty kraft paper or plastic sheet and clean the areas before painting) and use tack-rags to remove the dust from the surfaces

13.2 CLEANING AFTER SANDING
After sanding, the areas and surfaces must be cleaned thoroughly to remove the sanding dust. Use compressed air for seams and other parts where dust can settle. Remove dirty kraft paper or plastic sheet and use tackrags on the surface.

a Remove mechanically the oxide film on paint surface all over and “key” the paint surface using aluminum oxide paper grade 280 or finer.

b Clean the surface using white Scotch Brite Pads and water to remove dust and all contaminants.

c Alkaline clean per Para 11 on reworked surfaces and rinse with water. Ensure water-break free surface. Follow para 12 drying and solvent cleaning method prior to paint application.

14. PRIMER APPLICATION

14.1 APPLICATION EQUIPMENT (Options)

a) Conventional air spray
Atomizing air pressure: 60 to 70 psi
Pot pressure (if applicable): 5 to 20 psi

b) Air assist air-less electrostatic spray equipment
Fluid pressure: 850 – 1,000 psi
Atomizing air pressure: 65 – 75 psi
Tip size: 0.013 inches (0.33mm) or smaller, preferably .011 inch (0.28mm)

c) High pressure air-assist airless electrostatic spray equipment.
Fluid pressure: 2200 – 2500 psi
Atomizing air pressure: 60 – 75 psi
Tip size: 0.009 – 0.013 inch (0.23 – 0.28mm)

14.2 APPLICATION OF PRIMER
Observe General Notes.
Ensure surface is properly prepared and meets water break free test, fully dried and final tack solvent cleaned prior to painting. Apply one cross coat of primer.
Typical dry film thickness: 0.0005” to 0.0008”

Drying time: Re-coatable 1 hour (typical, see data sheet)
Dry to tape 4 hours. (typical, see data sheet)

14.3 ADHESION CHECK
After paint has dried check paint adhesion as per para 18.

15. TOPCOAT APPLICATION

15.1 APPLICATION EQUIPMENT

As per para 14.1

15.2 APPLICATION

Note: Observe General Notes.
Topcoat must be applied within 48 hours of primer application. If 48 hours is exceeded sanding of primer with scotchbrite pad (white) is necessary.
Apply one cross coat, or two coats of topcoat as required to achieve the desired finish.

Drying Time: Re-coatable 1 hour (typical, see data sheet)
Dry to tape 4 hours (typical, see data sheet)

15.3 ADHESION CHECK
After paint has dried check paint adhesion as per para 18.

16. CLEARCOAT APPLICATION
Topcoat must be treated with Aerodur Clearcoat UVR within 4 to 48 hours of topcoat drying if Clearcoat is called out in the drawing.
Apply two cross coats of Aerodur Clearcoat UVR over the topcoat.
Drying Time: Dry to tape 10 to 12 hours.
After paint has dried check paint adhesion as per para 18.

17. REWORK OF IN-PROCESS DEFECTS

a) In-process defects such as overspray, orange-peel, runs or sags occurring in the primers or in the topcoat which are considered excessive may be reworked by dry sanding with 240 grit or finer abrasive paper followed by wet or dry sanding with 380 – 400 grit or finer abrasive paper. (See para 13)

b) Sanding should not be attempted until the coating being reworked is sufficiently dry to permit sanding. This may take up to 8 hours depending on the weather.

c) After the sanding is completed, the surface has to be cleaned to remove the sanding dust. Use a cloth moistened with solvent cleaner and re-apply primer or topcoat, as required.

d) For some in-process defects such as overspray, runs or sags in finishing coats, it is possible to polish them away. Do not use ammonia-based polishes. Ammonia will destroy the gloss of most aircraft finishes. Only on high-gloss finishes, sags and runs can be removed by wet flatting with 1200 grit wet and dry paper and using clean water and soap. Use a non-ammonia polish with a fine cutting compound to remove the flatting scratches and a final cream polish to revitalize the gloss of the required area.

e) This operation can be done either by hand or polishing machine. When using a machine, a sponge head should be dampened down with water before applying the polish. This decreases the “burning” of painted surface.

18. QUALITY CONTROL

18.1 ADHESION TEST
Note: Tape adhesion test is to be carried after paint is fully dry. Refer to manufacturer data of specific paints used for “dry to tape” time.

a. Apply 1 inch wide 3M 600 Transparent Film Tape or equivalent to painted surface 1.5 inches long. Repeat this test with fresh tape on at least 3 locations some distances apart.

Note: Shelf life of tapes shall not be more than 6 months old from date of manufacture or as per manufacturer’s shelf life. Storage conditions at 70°F (21°C) and 40-50% relative humidity is recommended.

b. Press tape down firmly (5 pound minimum pressure)

c. Remove the tape within 5 minutes in one abrupt motion perpendicular to the paint surface.

d. Examine area for paint coating failure. Check tape for coating separation.

e. If there is an evidence of paint coating separation, determine extent of defective area and repeat para 8 when necessary.
18.2 WATER-BREAK-FREE-TEST
This must be thoroughly carried out for all large surfaces to be repainted to ensure good paint adhesion. Utmost care is to be exercised not to contaminate areas and tested to be water-break-free.

18.3 POST PAINTING INSPECTION

a Inspect painted surface visually to confirm no defects e.g. orange peel, runs, sags, contamination

b Ensure all mandatory and maintenance markings are re-installed correctly.

c Painter and LAE are to inspect for any damages to transparencies, composites and sealants by solvent and paint removers due to inadequate protection and/or the retention of these products in crevices

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