Stainless steels require oxygen (to bind with chromium to form a protective
chromium oxide layer) to work well. And even then they are susceptible to
chloride stress corrosion, crevice corrosion, and galvanic corrosion, especially
in oxygen poor stagnant areas (like inside bearings etc. Bronze is better,
monel or nickel-copper better yet, but all much pr icier.

That said, stainless steel can work satisfactorily but you have to use alloys
specific for the task. Don't use 302/304 series. The 316 series is better but
less strong and have been known to suffer catastrophic failure due to corrosion.
The best SS alloys are expensive and known by various trade names such as
Nitronic 50 or Aquamet 22. Those are the only SS alloys I would consider for
use below the waterline (but be prepared for sticker shock)

JJ


On Sat, 11 Oct 2003 12:15:24 -0400 (EDT), (Ron Thornton) wrote:

Cannons used to be cast out of bronze too until we learned how to cast
steel. My sailboat has the original SS shaft in sal****er for 25 years
and is doing fine. For a number of years now there have been a
gazillion shafts and props made of SS and I don't recall a lot of
problems with them.

Ron

James Johnson
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