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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
