Powder coating is really tough stuff. There is a guy around here that does the industrial type on rims,truck racks, ect but it is very thick and if you get much if any in the slide rails or ejector slot it can make your gun malfunction.
If you do decide to powder coat, let us know how it works out. I've wondered how well powder coat would hold up on a pistol, but I thought that the thickness as agentadam pointed out might make it impractical.Thanks.