Process practices for Black Oxiding??? 1

[tmox]

I am a contractor working for a client who requires that the project machinery be (matte) black for use in a darkroom environment.
As a matter of course, I spec'd black oxide finish for all steel parts, but, the client is concerned about the finish wiping off onto the users hands. I know what he means I have also seen (some) oxiding jobs that left a residue on your hands, but, i also know that this is not necessarily normal.
What i would like to find out is what to look for, what part of the process is critical in ensuring a residue free condition?

 

[unclesyd]

Depending on the quantity, you might checkout the following. We have used both companies products for years with excellent results. There is always something in the shop being blackened with a Birchwood Casey product. You can get your hands dirty but the coating will not come off.

http://www.birchwoodcasey.com/

http://www.heatbath.com/Products-link-page.htm

 

[BillPSU]

Powder coat would be my choice of finishes. Tough and durable.

 

[rorschach]

if you need parts hard and wear/corrosion resistant and still black, you might also look into Kolele's QPQ salt bath nitrocarbuizing process. while it won't be cost effective for everything, there could be situations where it might be useful (shafts, gears etc.).

 

[Flesh]

If black oxide is your choice for this application, then I would specify that the coating is produced to SAE-AMS 2485J. There are two keys to this specification. One, is that it is done above room temperature. I have run into problems when parts are processed utilizing a room temperature process (which really isn't black oxidizing), and is passed off as black oxidizing. Two, it is done in a liquid bath, not an atmosphere, i.e. a chemical process. I've run into heavy, flaking, oxide when it is processed via an atmosphere method. Asking the vendor to meet this specification, rather than asking for just "Black Oxide", should ensure a continuous, smooth, dense, and adherent coating.

 

[tmox]

thanx Flesh, that is exactly what i was looking for. While looking into this I also found a Mil spec # for B.O..
Mil-dtl-13924d - Coating oxide black for ferrous metals, and Mil-hdbk-205 Phosphate and Black Oxide coating of Ferrous metals.

cheers