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Problem: dezincification of brass in DI water service
Q. We have dezincification on our brass parts and we are having difficulty finding the root cause. Any thoughts? We are using D.I. water on the brass (CDA 260).
Arlette Puls- Antigo, Wisconsin
2004
A. CD 260 brass is 70/30 Cu/Zn. Dezincification is caused by the dissolution of zinc from the alloy to leave a very weak copper structure. It is sometimes seen in the UK in water fitments, especially in areas where the water composition is high in chloride and has other specific characteristics. It can be overcome by using a sacrificial aluminium anode, but this will be of no use to you with DI water - you clearly want pure water, not one that is enriched in metal ions! I would suggest you use plastic connectors for the DI.
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2004
A. Just in case you cannot change to plastic as Trevor said, could you change to bronze? It has virtually no zinc in it.
Guillermo MarrufoMonterrey, NL, Mexico
2004
A. Your material (70/30 Cu/Zn as per Trevor's post) is just ordinary cartridge brass and is not alloyed to prevent dezincification. There are plenty of specs for DR (dezincification-resistant) brass - which one you choose depends on what other properties are important to you (strength? machinability? colour? etc). The DR property is conferred by the inclusion of about 0.1-0.2 percent arsenic in the alloy formulation.
Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.
2004
2007
! In my experience with what appeared to be dezincification,
I concluded was copper immersion plate. When I went into a fresh sulfuric pickling solution with brass covered with oxide it would come out clean. But when I went into a highly used sulfuric acid solution it come out with a pure copper coating (the smut was analyzed and was found to be pure copper). I found pickling solutions with copper under 5 oz per gal. worked OK. On a lab scale I plated out the copper and found the sulfuric acid pickling solution to still work. Zinc and other metals will build up and one would have to determine how long you would be able to do this. My company closed before we were able to try it in production. I had proposed a continuous pumping into a side tank, plating the copper to keep it under 5 oz per gal and pump the solution back to the pickling tank. The copper plated out was found to be very pure [99.9+]. One has to think about the EMF the alloy has and the concentration of copper in the pickling solution. I think that's the heart of the problem. I hope this is somewhat helpful to someone.
Retired Chemist - Southington, Connecticut
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