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Zinc plating and black oxiding of powdered metal

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We want to zinc plate + black oxide seal some powder metal (MPIF 35, F-0008-25) parts. We need the black to look good aesthetically and not fall off in our hands. We need the parts to pass a fifty hour salt spray test. The parts are small, about on cubic inch, and all have an 1/2 inch through hole.

Grant Bryant
mfgr. - Indiana

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I have never heard of black oxide on zinc. It may be done, but I doubt it. Are you asking for a black chromate on it?

James Watts
- Navarre, Florida

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Zinc and black chromate should easily pass a 50-hour salt spray test when applied to a suitable substrate, Grant. However, depending on the quality of the powdered metal parts, they will probably be very porous, and could basically be unsuitable for plating onto. I'd suggest that you may need to investigate vacuum impregnation with a supplier to prepare the parts before plating.

As for the black oxide falling off, a true hot black oxide is not smutty like the cold blackening processes are. You may wish to see our FAQ on Black Oxide & Cold Blackening. Good luck.

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

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Message for Mr Grant Bryant

Vacuum Impregnation is an important prerequisite prior to any kind of plating operation for a sintered component. Vacuum Impregnation helps to seal the porosities in the components , so that the plating acids do not pose a problem of leaching after the plating operation is completed .

Best regards,

Mr Saibal Sen / Mr Probal Sen
Pune, India