The K-Coat aerosol spray finish is either very similar or to or is the replacement for a Gun-Kote product that I've used several times.
Both are applied to clean, degreased steel surfaces, and require "baking" in an open oven set to about 300 degrees F.
I used it to refinish a military FN49 rifle more than thirty years ago, and the finish has held up remarkably well. Except for handling scuffs and dings, it looks like it was applied last week. The original enameled paint was removed by boiling in lye solution and degreased thoroughly before application.
The several pistols I used it on were only "okay", because the coating apparently has only about as much scuff and abrasion resistance as teflon coatings. The .22 Hi Standard and .45 Government models I coated only held up to moderate use (a few weeks, maybe 100 hours holster wear) before bright spots showed on edges and curves.
As far as durability goes, my vote is for the Parkerizing or phosphate finish. If you have a commercial outfi do this, specify a military manganese phosphate with high wear and abrasion resistance. Refer to the military specifications for salt-spray durability and corrosion resistance.
