To expand on what Countryboy said, Parkerizing depends on a chemical reaction with the iron in conventional steel (it won't work on stainless for this reason) to produce the zinc or molybdenum (depending which type of parkerizing you use) crystals on the surface bonded and intimate with the iron in the base metal.
Doing it at home is common. I've used Brownells solutions with good success. Shooters Solutions has chemistries they claim are easier to use (they don't require atomized steel to initialize as the Brownells solutions do for best solution activity). In the case of their manganese type, Shooters Solutions include a certain amount of nickel to give a black color without a pretreatment as the more conventional solutions require.
I got a special tank welded up out of stainless for this activity; one long and thin enough to allow me to do a Garand barrel or operating rod in just one gallon of solution. It also has an aluminum heat spreader bolted to the bottom, which helps prevent burning the yellow precipitate the Brownells manganese type parkerizing produces. I use my tank over a double hot plate with an external temperature control. (You don't really need that last item; I just do it because I have such a control available.)
I originally used the stove, but my wife got unhappy about that approach. Same way she got unhappy about me bottling beer in the kitchen (sticky floor). I just had to go build my own facility or give up the hobby. You know how it goes. Great excuse to buy hammer drills and all the other fun stuff that goes with finishing out a corner of your basement.
Nick
