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Alternative method for blackening of iron and steel parts

2002

I know that Iron and steel parts are usually blackened with highly concentrated caustic soda [affil links] and Sodium Nitrate [affil links] sol' at 250 °F. This process is highly hazardous .

Some companies have come out with improved formulation. This not only operates at lower temperature but also at lower concentration. This has minimized the hazards and removed the possibilities of unwanted salt deposits.

Could you suggest us what it could be? How we can reduce the blackening temperature as well as time?

Vineet Lohiya
- JODHPUR, RAJASTHAN, India

Room temperature blackeners deposit a selenium compound onto the surface. The Metal Finishing Guidebook has an excellent chapter that covers everything about it except the exact chemical ratios, which are proprietary.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2002

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