I have toyed with the thought of Parkerizing the fasteners for my FAV project, the process is pretty easy and I am already set up for gun refinishing.
The process infuses oil into the surface of the metal giving it a tough and fairly corrosion resistant finish.
The only issue is the metal must be "virgin" so I am not sure how hard removing the original plating will be.
Parkerizing can be done in several "colors" from grey to black to green.
The military used to be big on cadmium which is a dull silver finish, I am not sure if that is the case any more as cadmium is a big taboo in the US as it is considered a hazardous material, but of course the "government" can ignore the rules the rest of up have to live by, there is a process called "copy cad" which mimics the cadmium finish, but again you must start with a "virgin" surface.
caswellplating.com