On Thu, 15 Jan 2009 10:54:52 -0500, "Joe AutoDrill"
wrote:

Just received a shipment of parts. I'm familiar with the brownish-black
"black oxide" method of coloring steel, but these came in glossy and coated
almost like a black anodized aluminum part... But not as durable as either
anodizing or oxide...


That sounds like what I know as black oxide. The glossiness is due to
a sealant applied after the oxide treatment. There are several
variables to control (temp, concentration, time, cleanliness), besides
the basic chemistry, so it's not unusual to see variations. One of my
customers put in their own line in order to control the process
themselves. They use the Penetrate Ultra Liquid on this page, after a
very thorough degreasing and cleaning routine. As advertised, the
parts come out a very dense black.
http://www.heatbath.com/heatbath/pro...ferrous_metals

--
Ned Simmons