At 09:31 AM 6/23/04 EDT, you wrote:
>I also have a powerboat here on the Chesapeake Bay, and we just replaced
>the "zincs", which I believe are Zamak castings. They are sacrificial anodes
>Pete
When a metal of high nobility is coupled with a metal of low nobility in
an electrlytic solution, especially seawater (but plain water will do), a
flow of electrical current will flow. Zinc is one of the least noble
metals and will create a relatively strong galvanic action with almost all
others and erosion of the least noble metal will occcur. This is why brass
(and zamak) isn't a good material for boilers.
I've never heard of anyone using sacrifical annodes in a copper model
boiler, there would be no compelling reason to do that, but that doesn't
mean it hasn't been done. In model steel boilers on the other hand many
people believe there is a benefit to sacrificial annodes, but then some
don't. I can't recall ever seeing an article where they were shown
conclusively to be necessary, but a few people believe in them and as far
as I know installing one doesn't hurt. The only problem could be that the
zinc molecules don't just disappear, they must go somewhere else within the
system, usualy to the most noble metal present, and will create deposits of
metal in places where they're not wanted.
Regards,
Harry
