How to Blacken Stainless Steel

Letter 0019

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Hello, I'm looking for information on the processes available for blackening stainless steel. If you could direct me to any publications or services, I would greatly appreciate it. Thanks,

Terry H
UC Santa Barbara

The Metal Finishing Guidebook lists 3 formulations of blackening baths for stainless steel, Terry. The one that sounds simplest to me, although I can't comment on its efficacy, reads:

Sulfuric acid, 180 parts( Sulfuric Acid 93-98%. Size 2.5 L[link is to a source of concentrated acid; this is for people trained in its safe handling only!])
Water, 200 parts
Potassium dichromate, 50 parts (Potassium Dichromate [link is to product info at Amazon])
Operating temperature, 210 degrees F.

 

Proprietary processes are available from such suppliers as:

Electrochemical Products Inc. (EPI) and

Heatbath

There are also stainless steel anodizing processes offered by B&M Finishers and a stainless steel black passivation process offered by Russamer Labs. Good luck.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

Terry,

Your question did not specify what purpose the blackened stainless steel is to be used for.

Some of the components inside a TV tube must be "blackened" using a process of heating and cooling in a controlled atmosphere.

Leslie R Williams
- England

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Ed. note: You're right, Leslie. People get the most rewarding answers to their questions when they employ the reporters' creed of "who, what, when, where, & why" when posting :-)