G. Clean the surface to be painted using solvent, Series 84 (Ref AMM/SOPM 20-30-84) until no visible residue appears on cheesecloths used to wipe the surface dry.
H. Abrade stainless steel and titanium surfaces with 180 to 320 grit silicon carbide paper.
CAUTION: SEALANTS AND SMOOTHER CAN BE DAMAGED DURING PREPAINT CLEANING OPERATIONS. DAMAGE IS DEFINED AS VISIBLE SEPARATION OR LIFTING FROM THE EDGE OF THE SEALANT. DAMAGED SEALANT/SMOOTHER WILL NOT READHERE AND MUST BE REMOVED.
(1)
Separation confined to the thin edge of the sealant fillet, not extending to the body of the fillet, shall be removed by abrasion with Scotchbrite pads.
(2)
If separation occurs between the body of the sealant fillet and the airplane skin, remove the damaged (separated) part of fillet.
NOTE: The sealant fillet can be separated from the skin during cleaning with solvent. Test the adhesion of fillet to skin with fingernail, knife, etc.
(3)
Repair sealant as required (Ref 51-31-0, Seals and Sealing).
I. Do not abrade aluminum flame sprayed fiberglass. Alodine 1200 treated surfaces need not be abraded nor realodined.
4. Surface Pretreatment
A. Pretreatment Method I (prior to application of a wash primer system): Thorough Scotchbriting
CAUTION: DO NOT DAMAGE SEALANT FILLETS IN BONDED LAP JOINTS. IF DAMAGED, REPLACE.
(1)
Wet abrade thoroughly to an overall satin finish using Scotchbrite pads and solvent, Series 84 (Ref AMM/SOPM 20-30-84).
(2)
Solvent wipe with solvent, Series 84 (Ref AMM/SOPM 20-30-84) to remove all residues, wiping dry before the solvent evaporates. Repeat as necessary to remove all sanding residues.
(3)
Allow the airplane surfaces seams and lap joints to dry thoroughly prior to priming.
(4)
Apply wash primer (Ref 51-21-171, Decorative Paint System).
B. Pretreatment Method II (prior to application of an epoxy primer system) Alodine 1000, or Alodine 1200 (Alodine 1200 is preferred):
CAUTION: DO NOT DAMAGE SEALANT FILLETS IN BONDED LAP JOINTS. IF DAMAGED, REPLACE.
(1)
Wet abrade thoroughly to an overall satin finish using Scotchbrite pads and solvent.
(2)
Wipe the surface using cheesecloth and solvent. Repeat as necessary to remove all sanding residue.
(3)
Flood the surface with clean water until a water break free surface is obtained. A water break free surface will maintain a continuous flow of water for 30 seconds. If a water break free surface is not obtained, repeat wet abrasion and rinsing.
(4)
Prepare, or store if required, Alodine 1000 or Alodine 1200 solution per 51-21-41, Alodizing.
(5)
Apply Alodine 1000 or Alodine 1200 solution per 51-21-41, Alodizing.
(6)
Allow the airplane surfaces, seams and lap joints to dry thoroughly prior to priming.
(7)
Apply BMS 10-11 primer to interior surfaces (mask exterior surfaces) (Ref 51-21-171, Decorative Paint System).
(8)
Apply BMS 10-79 primer to exterior surfaces (Ref 51-21-171, Decorative Paint System). Previously Painted Surfaces
(1)
Epoxy primed surfaces
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51-21-21 Page 702 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. May 01/98
(a) Sand with 400 grit or finer aluminum oxide abrasive paper as required to remove surface roughness and loose soils. Just prior to over-coating, wipe with tack rags to remove dust and lint.
NOTE: Rough surfaces such as castings, forgings, etc., which cannot be sanded without exposing the base metal shall either be tack ragged or solvent cleaned, whichever is applicable. Sanding such surfaces should be avoided.
(2)
Prestec radome coating less than 12 hours old
(a) No treatment necessary.
(3)
Prestec radome coating greater than 12 hours old
(a) Treat per step 4A (2) except use naphtha in place of solvent.
5. Detailed Instructions for Prepaint Cleaning and Pretreatment of Plastic Surfaces
A. Unpainted plastic surfaces with surface porosity (i.e., pinholes)
(1)
Remove greases and other contaminants from surface to be coated by scrubbing with a clean cheesecloth saturated with toluene. Wipe the surface dry with clean cheesecloth.
(2)
Structural and Nonstructural Laminates
(a) Hand-sand the surface with 240 grit or finer abrasive paper to remove any glossy finish of the laminate. In sanding, do not abrade the glass fiber reinforcement. Remove sanding dust by wiping the surface with a tack rag or clean cheesecloth wet with solvent. Before solvent evaporates, wipe surface dry with a clean dry cheesecloth.
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