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Treating old Beechcraft "V-Tail" Bonanza magnesium Flaps bare metal before painting

2007

Hi, I'm Thom an aircraft mechanic. A Beech Bonanza owner asked me to strip & paint his wings from a very early model "V-Tail". It turns out his Flaps & Ailerons are magnesium. There's a fair amount of surface corrosion on the skins and I've sanded the parts with 320 and 400 grit aluminum-oxide but now I need to pickle the skin before I spray the Epoxy Primer & Polyurethane Topcoat. Mfg's Manual calls for a mixture of Chromium Trioxide & plaster of Paris solution in water applied to the skin, a kit called Dow19 however I can't find it anywhere and I have to treat these surfaces pronto !

Can anyone out there tell me where I might secure this Chromium Trioxide or Chromic Acid (technical-grade) or DOW19 kit ?

Does anyone else know of another corrosion inhibiting process that would allow me to paint over it once it's applied ?

Thom Barlow A&P IA
FAA Certified Aircraft Mechanic - Wesley-Chapel, Florida, USA

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First, be aware of the many EPA and OSHA restrictions on the traditional hexavalent chromium processes for magnesium.

See letters #20396 and 43297 for magnesium pretreatment info. Also, SanChem has a a chrome-free conversion coating for magnesium, SafeGard 3400Mg.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2007

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Thom,
The mag has to be chromated (Alodine). Aircraft Spruce most likely has it, but an expert in this field is Neil Pobaanz of the American Bonanza Society. Phone number there is 316-945-1700.

Good Luck and keep that Bonanza flying!

Trent Kaufman
electroplater - Galva, Illinois
2007