Home /
Search 🔍
the Site

World's #1 finishing resource since 1989
No login needed: Chime right in

topic 1011

Zinc-Cobalt as a replacement for Cadmium Plating


Is there any current information on the use of electrodeposited zinc-cobalt, ASTM B840 [affil. link to spec at Techstreet], as a replacement for cadmium plating, QQ-P-416 [link by ed. to spec at Defense Logistics Agency, dla.mil] F, on fasteners?, in the aerospace industry? Also, where does zinc-cobalt fit in the galvanic series with respect to aluminum alloys-5052, 6061, etc..

Joe Pesik

March 13, 2010

Hi, Joe. The idea behind zinc alloy plating is that, by carefully choosing the percentage of metals in the alloy, it is possible to get the galvanic voltage closer to where you want it than the fixed galvanic voltage of pure zinc. Zinc alloy plating is completely proprietary as far as I know, so I'm confident that the supplier of the process can tell you the galvanic value of their alloy.

Replacing cadmium is always difficult because it's not just one property, like galvanic potential, it's corrosion resistance, lubricity, compatibility with aluminum, freedom from bulky corrosion products, good stick-slip performance, malleability, etc. It's worth the effort but not easy, and I doubt that you will find something that says it's okay to do the replacement as a matter of spec. More likely is probably that new designs will be spec'd for zinc cobalt rather than finding a blanket statement that it's okay to substitute zinc-cobalt for cadmium. Good luck.


Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

finishing.com is made possible by ...
this text gets replaced with bannerText
spacer gets replaced with bannerImages

Q, A, or Comment on THIS thread SEARCH for Threads about ... My Topic Not Found: Start NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories:

Chemicals &
Consult'g, Train'g
& Software

About/Contact    -    Privacy Policy    -    ©1995-2021 finishing.com, Pine Beach, New Jersey, USA