Considering my first airbrush

Stores that sell auto bodywork supplies and paints are a good source for info and materials. I bought a spray can of Etching Primer from one of them that is ideal for aluminum and other metals. As Don advised, cleaning with a good solvent is also important, as is scuffing the surface with a very fine abrasive pad, also an auto body product. At the very least, dip your bolts in vinegar and rinse - it's the low buck etch for zinc plated hardware.

Hope this helps, and Happy Holidays!

Mike

Airbrushing won't help your problem.  The problems with painting metal are cleaning and priming.  Many metal parts end up with an oily surface either because of the forming operations, or preservatives.  Also paint does not like to stick to metal.  Cleaning requires a good solvent, and the primer should be specifically a metal primer.  Red oxide primers are good for steel.  Aluminum is harder to find a good primer for, since zinc chromate became controlled as a health hazard.

This site offers some nice points on choosing an airbrush

sites.google.com/.../donsairbrushtips

I considered anodizing but it might be too expensive. Ironically, I hadn't thought about just buying Testors enamel and using that. That worked great and it went faster than I thought it would once I got a board set up to hold all of the screws. Now hopefully they look decent after I put them in my board - I shouldn't have to use a wrench since I'm going to tap the holes first... we shall see!

... but I still want an excuse to buy an airbrush...

I'm not sure airbrushing would help. The flaking is probably from flexing material and hard pressure.

Maybe you should look into if anodising might be a better, more durable solution.