Best corrosion protection method for steel parts?

I recently purchased a partially-completed 750 kit. I'm well in to the fuselage build and using Cortec, but have yet to have to install any steel parts. The previous builder did not get the powder-coat option, so I'm concerned what is the best method to protect the steel parts? I know some parts will not be subject to getting nicked and chipped, so I "assume" even just a zinc chromate/phosphate primer would be sufficient?

However, obviously the control sticks, rudder pedals, gear fittings, etc. WILL be exposed to chipping and wear, etc., so I "assume" (again!) that powdercoat or 2-part epoxy type paints would be desireable. I'm considering painting the aircraft myself when completed (I've sprayed a car before), but presently have no equipment.

Soooo, all that being said, any recommendations for protecting the steel parts? Powdercoat everything? Zinc chromate on some stuff and epoxy or powdercoat on other exposed parts? (obviously if I go the epoxy primer route, I should bite the bullet and get a sprayer - although I did brush epoxy primer (Corlar)on chrome-moly tubing and it didn't look too bad!)  I've even seen some advocate "POR 15" - supposedly very tough, non- chipping finish.

 

Regards,

John

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Permalink Reply by Phill Barnes on May 30, 2011 at 6:38am

Hi John

I have used 2K epoxy primer surfacer with 2K polyurethane over the top. Shamfully my aircraft is a few years old and never flown owed to personal circumstances but to date there is absolutely no evidence of any corrosion whatsoever. My aircraft gets it's share of moisture as my shop gets 1/2" of water across the floor whenever it rains and it rains a lot. For abrasion resistance on things like rudder pedals torque tubes and control sticks, I would think that chrome plate would be best and on the cabin parts infront of your face although I would probably just use a 2K gloss black on those parts.

 

Phill

Permalink Reply by Geoff Klestadt on May 30, 2011 at 1:57pm

Best I've seen for steel is a zinc rich epoxy primer (mil p 46105) with the top coat of your choice. The zinc particles are a form of cold galvanising that protects the bare metal if its scratched.

 

http://www.pwpaints.com/acprimers.html

http://www.pwpaints.com/acprimers.html#46105

 

Electroplating or using a phosphate based acid etch primer on 4130 steel leaves open the possibility of "hydrogen embrittlement" which is apparently not a good idea.

http://en.wikipedia.org/wiki/Hydrogen_embrittlement

 

http://www.eaa1000.av.org/technicl/4130.htm

Permalink Reply by John Austin on May 30, 2011 at 7:25pm

Phill,

I didn't realize that you could get a true 2-part epoxy in an aerosol can!  That looks like a really good solution - even if I had spray equipment, it might be worth using a can or two on small parts just to avoid the spray gun cleanup! I understand it has a 4 day pot life after activation, but if one prepped all the parts and had everything lined up and ready-to-go, you could just keep painting until the can was exhausted.

How did you prep the metal for painting? I've seen a suggestion that clean steel can just be scrubbed with steel wool and acetone.

Regards,

John

Permalink Reply by Jan van 't Schip on June 1, 2011 at 11:26am

I had my steel parts black zinc coated, except for the cabin frame. See http://www.zenith.aero/photo/steel-parts?xg_source=activity

 

The layer is thin; no problems if the steel part has to fit in a bearing, like some steel  parts do.

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