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AMT 111 Aircra* Pain-ng and Finishing Chapter 8 •  Purpose ! 
Paint Protec-on •  Corrosion •  UV protec-on ! 
Fabric Composites Aerodynamics !  Looks ! 
•  Follow pain-ng instruc-ons to the leCer •  Video •  Protect yourself Paint Eye !  Respirator ! 
•  Good ven-la-on ! 
Gloves •  Dangerous chemicals •  Oils on the paint surface •  Correct pain-ng environment Clean !  Clean !  Low humidity and correct temperature ! 
Paint Removal From Metal •  Video •  Protect plas-cs and rubber Remove antennas !  Remove or cover fiberglass parts !  Cover -res !  Cover rubber seals with aluminum tape !  Cover windows with aluminum foil !  Plas-c shee-ng can also provide good protec-on !  Paint stripper will seep through paper ! 
•  Protect lubricated joints ! 
Strippers will dissolve grease/oil •  Chemical Strippers Match stripper to paint !  If applied with brush, brush only one direc-on !  Cover with plas-c to keep it from evapora-ng !  Wait un-l paint is loose ! 
•  Enamels will bubble •  Lacquers will just so*en ! 
Removing loose paint •  Plas-c/wood scraper •  Plas-c brush or Scotch-­‐Brite •  Steam or power wash •  Never use steel wool or brush •  Chemical ! 
Strippers Remove wax le* behind from stripper •  Use MEK or acetone •  Don’t use lacquer thinner (will not remove wax) ! 
Don’t use on fabric or fiberglass •  Can dissolve underlying adhesive •  Mechanical ! 
Strippers Abrasive material is used to blast off paint •  “Sand blas-ng” •  Aluminum oxide •  Plas-c beads •  Baking soda •  Dry ice •  Don’t mix abrasives used on steel and aluminum Too harsh for sheet metal !  Good for small parts !  Good for steel tube ! 
•  Video •  Primary func-on ! 
Priming Bonding between final “color” coat and base material •  Metal, fabric or composite Corrosion protec-on !  UV protec-on ! 
•  Water test – water will form a film on clean metal ! 
If the water film “breaks”, the surface is not clean Priming •  Conversion Coa-ngs For aluminum !  An acid that causes a chemical reac-on that creates a protec-ve coa-ng on metal ! 
•  Also provides a rough bonding surface by chemical etching ! 
Alodine -­‐ a chromate coa-ng – yellow/gold •  Can be the only finish Phosphoric acid – creates a phosphate film !  Primer can be applied over conversion coa-ng ! 
•  Wash Primer Priming For aluminum !  MIL-­‐P-­‐15328 – Polyvinyl, zinc chromate, magnesium silicate, phosphoric acid and alcohols !  Greenish-­‐amber !  Spray on light coa-ng !  Let dry for 30 minutes !  Apply topcoat within 8 hour ! 
•  A*er 8 hours, reapply second coat •  Wash Primer ! 
Priming Humidity/water control is cri-cal •  Follow instruc-ons for correct humidity/water combina-on •  Applica-on in low humidity with inadequate amounts of water will lead to corrosion Can be followed by a tougher primer like epoxy !  Epoxy can be applied to a wash coa-ng that has dried over 8 hours !  Heavy metal content may limit future applica-on ! 
•  Zinc Chromate Priming Can be used on most metals !  Yellow or dark green !  Can be sprayed directly on metal !  Inhibi-ve primer – inhibits corrosion through chemical reac-on ! 
•  More than just a barrier If applied over a wash primer, the wash primer must be completely dry to prevent water entrapment !  Don’t use with acrylic lacquers !  Heavy metal content may limit future applica-ons ! 
•  Epoxy ! 
Priming Two part mixer •  Follow instruc-ons exactly •  May require thinner and/or retardant Tough !  Good for all metals and composites !  Follow drying instruc-ons exactly ! 
•  Only “par-al” drying for some top coats •  May need sanding, to scuff up, if le* to dry too long ! 
Can be sanded •  Acrylic Lacquer ! 
Top Coats Solvent based •  May dissolve zinc chromate primer •  Low color solids requires several light coats Retarder helps final coat flow !  Older style paint ! 
•  Synthe-c Enamel Pigments suspended in resins !  Cures by oxidiza-on ! 
•  Polyurethane ! 
Top Coats Two-­‐part •  Follow instruc-ons exactly •  May require thinner and/or retardant Chemically cured !  Tough ! 
•  Abrasive •  Chemically ! 
Slow drying encourages flowing •  Helps smooth out surface May be part of complete system that includes the primer !  Video ! 
Fabric Finishing •  Acetone can be used to remove oils/grease from fabrics ! 
Resist the tempta-on to touch the fabric with you bare hands •  CoCon or linen requires a first coat that includes fungicide •  Nitrate is a wonderful explosive ! 
During sanding, protect from sta-c electricity by grounding or wet sanding •  A coa-ng containing suspended aluminum flakes/powder is used to block UV light •  Video •  Video Repairs •  Avoid them: ! 
Paint Problems Cleanliness •  Grease, oil, and dirt •  Dust and dra*s •  Air supply Follow direc-ons !  Light coats ! 
•  First coat should be a light “tack” coat •  Use light cross coats in place of a single heavy coat ! 
No zebra stripes •  Avoid them: ! 
Paint Problems Organiza-on •  Have material ready •  Walking space for pain-ng (do a walk through) •  Easy access cleanup ! 
Smooth gun ac-on •  Filter paint as you fill gun •  Correct distance •  Straight •  Prac-ce on scrap •  Clean •  Blushing ! 
Paint Problems Water vapor trapped in paint •  Worst on rainy and high humidity days Dull, cloudy, porous finish !  Add retardant to slow down drying ! 
•  Pinholes Too hot to spray !  Too much solvent !  Too high air pressure ! 
•  Fisheyes ! 
Oil, grease, wax or silicone (some rubbing compounds) •  Orange Peel Paint Problems Too liCle thinner !  Too much paint !  Too liCle air pressure !  Wrong nozzle ! 
•  Runs, Drips and Sags Too much paint !  Gun too close ! 
Paint Problems •  Bad Masked Edges ! 
Tape le* on too long •  Sharp edges •  Tape stuck in paint •  Remove as soon paint is tacky Cheap tape and paper !  Tape correctly applied ! 
•  Use small tape for sharp changes ! 
Follow up with larger tape Video • 
LeCering Layout 14 CFR Part 45 defines registra-ons markings Standard high is 12” Standard leCer is 8” wide “M” and “W” are 12” wide “1” is 2” wide Spaces are 2” wide Spray Gun •  Video one – 12 min •  Video two – 12 min