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Differences between black oxide and phosphating processes

Q. Dear Sir,
I want to know the difference between the Blackening and phosphate coatings on a hydraulic vane pump.

Bindu

Bindu Karipoola
- Hyderabad, A.P., India
December 24, 2011

Hi, Bindu.

Black oxide (with wax or oil) is usually a final finish. Phosphatizing is usually for surfaces which will be painted.

However, if you are talking about the internal parts of a pump, they are sometimes phosphatized for oil retention. Picture the parts during initial startup or after a prolonged downtime . . . phosphatizing can prevent the galling of metal to metal contact.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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December 26, 2011

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