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Posted by Chriscase [76.243.31.20] on Friday, September 04, 2009 at 17:01:09 :
In Reply to: Re: Priming small parts posted by Doc Dave [66.82.9.54] on Friday, September 04, 2009 at 08:37:36 :
I use a gallon of "Plumber's Lime Remover". It is Phosphoric acid solution for removieg lime and scale around fixtures, off tile, etc. Then I add some zinc bits that I have accumulated- broken pot metal castings of any ilk. About the size of a one ounce lead sinker, in bits. Leave the lid loose, it will foam up some in the first day or so. Put it where the escaping foam won't leave white deposits on concrete, or discolor wood.
In use, on any bare steel surface, soak it a few hours or rag it onto big stuff. It will dry, but be gummy, it needs more water. Wet it, or apply more. May need to wet with water second time. If it dries gummy, again. The water tries to leave before the acid does it's job. But once the acid has finished, it leaves just a bit of a galvanized surface. You'll see a different, zinkier color.
There is a proprietary system for this, called "Parkerizing". Next step would be to oil the parts and roast at 350°. That leaves a greenish tinge, maybe zinc phosphate?
My 5 gallon bucket has enough dissolved rust and metallic paint residue in it that now the parts come out black, and 'sooty'. Wire brush in water cleans the soot off, leaving the black. Iron phosphate coating?