Metal finishing Q&As since 1989

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Blackening stainless steels

2007

Can the black oxide (hot or cold process) be used to provide a permanent deep rich black/brown finish on stainless steels (austenitic, ferritic and martensitic all inclusive).

Also, will a pre-treatment of a full electro-polish prohibit the blackening process?

Thank you,

Phil Parsche
finishing services - Pleasant Prairie, Wisconsin, USA

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Doubtful that anyone will guarantee "permanent deep rich black/brown finish...all inclusive."

Electropolishing shouldn't prevent blackening although may require slightly longer acid pretreatment as it leaves a thin (~10 nm) Cr-enriched surface. I do not expect electropolishing time to have much effect, as at steady state the surface alloy is uniformly removed.

You probably need to send out various stainless samples for blackening. Read MIL-DTL-13924 [on DLA] COATING, OXIDE, BLACK, FOR FERROUS METALS for precautions regarding hardened martensitic stainless & warn the vendor accordingly.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2007

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You might want to check into PVD titanium black stainless steel.

Michael Liu Taylor
specialty stainless steel distributor - Dallas, Texas
2007