I was talking to someone about anodizing and ended up drawing some quick diagrams. Thought I'd include them here for people to have an idea how keyboard parts can be anodized.
Firstly, only aluminum and a few other metals (like magnesium and titanium) can be anodized--stainless steel bolts and other parts will be corroded by acid in the anodizing bath and should not be included with your keyboard case. Aluminum bolts are safe to leave in your part, if you'd like them to be anodized and dyed to match. Type II and III anodizing are the typical ones seen on aluminum keyboards, and they are done in sulfuric acid baths with an electric current flowing through. Type II gives a typical thickness anodized layer, and type III is a thicker layer--what's known as hard anodizing. Anodizing does not grow an extra layer on top of a surface--it actually transforms the surface of aluminum to a certain depth. So subsequent peeling and reanodizing will diminish the size of your part, albeit by a microscopic amount. But with enough reanodizing, you can notice that your bolt will fit a bit loosely in the reanodized threaded holes. Good article here:
http://en.wikipedia.org/wiki/AnodizingOne of the tricks to an even finish is to properly suspend your keyboard part in the anodizing bath as well as in a dye bath. Finish/texture are important too, so your part should be polished or sand/bead-blasted first for an even color. If you're reanodizing an already finished part, you don't really need to worry about it where chemical stripping is possible, unless there are scratches or dents present--then you might need to re-finish as well.
Because anodizing and dying is done via contact of acid and dye with the surface of your aluminum parts, it's important to suspend those parts strategically, as anywhere you touch those parts, anodizing and dying will not happen properly. Typically, anodizing racks are used to suspend aluminum parts in acid and then subsequently in a dye bath on the same rack, without having to touch that part by hands at all. I drew this quick diagram of a typical anodizing "rack", and hopefully it's comprehensive enough
Those rings with spiky spokes can be adjusted up and down, and your part can be inserted onto them and held via tension/friction. There will remain tiny silver pin-prick dots on the anodized surface where where the rack touches it. If you are giving your keyboard parts to someone to anodize/reanodize, you should inquire what sorts of racks they use and think about the best way of putting your parts onto them, to make sure the points of contact are well hidden. Anything like a wire through USB port and what not can damage those openings but also prevent the USB port area from getting an even color/anodizing layer. It's also possible to suspend your part via attaching something to aluminum bolts inserted into it, but you'd have to find some sort of non-conductive string that won't corrode in sulfuric acid... or some sorts of aluminum hooks you can attach to your aluminum bolts.
Initially, when your part is anodized, it's the standard color of anodized aluminum (silver or dark gray, or champagne, or whatever color depending on alloy and anodizing thickness). The newly-anodized layer is porous until sealed. It can be dipped into specialized dye immediately after anodizing (can be as simple as RIT dye, though specially formulated anodizing dyes are better quality and will have more intense / interesting effects and should be preferred) and sloshed around (or left in an agitated solution of dye) for anywhere from ~2 to 20 minutes, depending on dye concentration and desired color intensity. Then, when the part has been dyed (or just left as is), it is dipped into a solution that seals the pores and rinsed--and that's the end. You can handle it and and attach to your keyboard at that point.
