Powdercoating Specifications 1

[uGlay]

I am sending some parts out for quote. They will be mounted on the exterior of the aircraft. What is the most common powdercoating conventions for exterior parts? Color will most likely be white. I have accounted 0.010 globally for coating thickness.

Any direction is greatly appreciated.

Cheers, UgLay.

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[bf109g]

My experience has been that if it's metallic and going to be mounted on the fuselage exterior, like a doubler, it should have the same coating system as the fuselage. That generally consists of a primer, paint and a topcoat. It also eliminates coating compatibility problems that can result in loss of paint and primer and an invitation to corrosion.

Of course, that doesn't hold true for anything hat has to transmit/receive. Antennas shouldn't be touched due to transmissivity requirements. Antenna support structure should have the same coating system as the fuselage for the reasons I mentioned above. You also have to consider electrical bonding of the antenna to the airplane. Will a powder coated doubler affect bonding?

To answer your question, MIL-PRF-24712 is the only standard I'm aware of. Powder coating is entirely dependent on the facility and equipment.

 

[der8110]

powder coating?

with any discontinuity (even a thin corner) it can trap moisture underneath, kids' playground equipment shows that.

 

[uGlay]

bf109g thanks for the information.

der8110 what alternatives do you recommend?

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[TVP]

The alternatives depend upon what you are painting (material, shape, etc.). The typical aircraft coating sequence is pre-treatment + primer + topcoat. Pre-treatment for Al alloys is a conversion coating according to MIL-C-5541 or MIL-DTL-81706. Typical primers are epoxies, either high solids according to MIL-PRF-23377 or waterborne according to MIL-PRF-85582. A typical topcoat would be polyurethane according to MIL-PRF-85285. The US Air Force specification TO 1-1-8 is good source of information for aircraft painting. The following links have more information, including the actual specifications mentioned above:

http://assist.daps.dla.mil/quicksearch/

http://www.robins.af.mil/shared/media/document/AFD-070108-244.pdf

http://www.corrdefense.org/Academia...0850Adv_Aircraft_Corr_Prot-Osborne-Boeing.ppt

http://acqp2.nasa.gov/workshop2006/...ngs and Decoatings Specifications Updates.pdf

 

[uGlay]

The part is an adapter for an ELT antenna. It is 2" tall, aluminum and will be mounted on the tailcone of the aircraft behind the vertical fin. the tailcone is made out of carbon fiber composite and we will be attaching the adapter mechanically. The question I have is, which would be the appropriate spec for this part?

I sent out some files to a couple of machine shops and they are not really sure what to do about the MIL-PRF-24712 specification.

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[bf109g]

Bad place to put an antenna due to flow around the stab and fairing...

I would investigate the coating system on the tailcone - fuselage interface (if the fuselage is aluminum) and copy it.

 

[uGlay]

I know it's a bad place but it isn't my call so I just gotta work with what I got.

I'll look in the SRM and see what kind of specs I find for existing finish.

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[bf109g]

I'd also look for tailcone repairs - you are going to need them.

 

[uGlay]

If the installer breaks the tailcone, that isn't really my problem.

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[uGlay]

You guys are taking this thread off topic.

The matter at hand is the powder coating, not any of the technical aspects that an ELT antenna install require.

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