Effects of Zn Yellow Dichromate Fasteners on 6061 T6 Aluminum
I want to use zinc yellow dichromate stell rivets in an AL 6061 T6 housing. What type of galvanic corrosion effects can I expect?
DonDonald D. Barnard
- Hanahan, South Carolina
At the risk of sounding snippy, what are yellow dichromate stell rivets?Robert M. Wilson
aerospace - Wichita, Kansas
"The Opinions Expressed herein are my own and not those of my employer"
I'd say that, stell is a typo, and since steel cannot be dichromated, Mr. Barnard is referring to steel rivets that have been zinc electroplated and then passivated with hexavalent yellow chromate (dichromate).
Zinc plated fasteners are not fully compatible with aluminum. You would not use them on an airplane skin for example; that could be a disaster. In such a case you would need cadmium plating (environmental no-no to be avoided if there is any other way!) or IVD aluminum plating or such. Your question is perhaps a practical one, though, where you are asking "how bad is it?". Well, aluminum electronic chassis used in protected environments frequently use zinc plated fasteners. In a dry, air conditioned environment you might not see any corrosion at all after many years. It's just a very difficult question to answer if you are building something of moderate price.
Ted Mooney, P.E.
Pine Beach, New Jersey
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