Re: what is parkerizing or bluing & how is it done (chemical processes)?

Both "Parkerizing" and bluing involve multi-stage processes.  Both usually 
begin with an aqueous alkaline cleaning stage (~150°F)followed by water 
rinses.

"Parkerizing" is sort of a brand name used to refer to zinc or manganese 
phoshate processes (like saying Coke to refer to cola).  A zinc phospahte 
bath consists of zinc oxide disolved in a phosphoric/nitric acid 
solution.  Zinc is relatively non-soluble, but stays in solution at a low 
pH.  When the acid attacks the metal, the pH rises at the metal surface, 
causing the zinc to precipitate onto the surface as zinc phosphate 
crystals.  This is followed by another rinse.  Manganese phosphating works 
the same way.  Both produce dark gray coatings.

"Bluing" of metal is done by exposing the metal to a high temperature 
(>220°F), alkaline solution of various oxide compounds.  A black oxide is 
formed on the surface (Fe3O4, as opposed to Fe2O3, which we know as 
rust).  Different salts in the solution (Mn, NO3, etc) give different hues 
to the coating.  This stage is then followed by a rinse.

I wouldn't recommend trying either of these processes on your own.  Both 
involve dangerous substances and high tempertares.  Many companies who 
offer these services can be found on the internet .

Mike Raab