Where the
world gathers for metal finishing
Q&As since 1989


-----

Sulfur Depolarized Anodes for Nickel Strike

I would appreciate if anybody could tell me what is the sulfur depolarized anode which is used in nickel strike, and how can I make or buy it. Thanks

N. Dadvand
- Halifax, Canada
2000

---

A sulfur depolarized anode has sulfur cast into it to aid in anode corrosion and keep the anode from going passive. Inco can supply them. You can also get them from an anode supplier like Carter Alloys Company [a finishing.com supporting advertiser] or Tally Metal Sales.

But, to my knowledge, a strike bath usually operates at a sufficiently low pH that passivity is not usually a problem and regular pure nickel anodes are usually used to avoid nickel buildup.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2000

----
Ed. note: Inco no longer exists but became part of Vale Limited; sorry, we don't know whether nickel anodes are in their Vales's product line anymore.

SD nickel should not be used in a woods strike tank. Your nickel content will rise much faster and the sulfur is a slow poison for the tank. Using SD will make the tank stink, turn a dirty dark color and require considerably more filtration and carbon treatment and will still have to be replaced much sooner for adhesion related problems.

James Watts
- Navarre, Florida
2000

I agree with both Ted and James. However, it is not necessarily the pH that determines the passivity of regular nickel. The most important component for dissolving regular nickel is the chloride content of the bath. As long there are sufficient chlorides in the bath regular nickel should dissolve just fine. SD nickel was developed and is used extensively in electroforming where controlling plating stress requires baths of low or no chloride content.

Don Piett
INCO Ltd - Thompson, Manitoba, Canada
2000