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Rusting found on 303 S/S Fastener, Passivated and Black Oxide

Rusting found on 303 S/S Fastener, Passivated and Black Oxide

Rusting found on 303 S/S Fastener, Passivated and Black Oxide

To all and sundry:

Has anybody found that they have had corrosion difficulties with stainless steel fasteners (303) that have been passivated and then coated using black oxide.  We have found that rusting (red corrosion) starts on the machined aspects of the fastener at about 48 hours.  We have sent samples from two different lots out to an AL2A lab and have gotten the same results from Salt Spray testing (ASTM B117-1997).

Best Regards

RE: Rusting found on 303 S/S Fastener, Passivated and Black Oxide

Dear Randy;

I found this information at clevelandblackoxide.com

"New materials technology gives processors such as Cleveland Black Oxide a competitive edge. As noted by Dave Tatham, president of Cleveland Black Oxide, "Black oxiding produces a microporous surface that will readily bond with a topcoat. We can now add a supplemental oil topcoat that boosts salt-spray resistance to the same level as that of zinc plate with a clear chrome coating (100 h) at less cost."

Hope its helpful


RE: Rusting found on 303 S/S Fastener, Passivated and Black Oxide

If the black oxide is iron oxide, it is a powerful corrosive agent for stainless steel. 303, with its high sulfur, has enough problems in this regard anyway.

RE: Rusting found on 303 S/S Fastener, Passivated and Black Oxide

I recently had a part coated with black oxide per AMS-2484-H.  My specification was to AMS-2485-C.  I cannot find a copy of the revisions so I can determine what has changed from Revision C to Revision H.  Can anyone help?

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