"Sailboat Restorations, Inc." wrote: [Re: my assertion that SS cable was susceptible to crevice corrosion.] > That's interesting. What tome is this? I have the Caribou, as well, so I > am a bit concerned. But I have been working on sailboats for many years, > and I have never heard it said that ss exposed to salt water "is notorious > for its degradation." Quite the contrary, I have always understood that ss > is one of the best substances to use in a marine environment, second only to > bronze, and preferable to bronze where certain types of strength are > required. Indeed, most modern sailboats use little or no bronze, and use ss > for most everything. For example, most sailboats use ss prop shafts. These > are actually *under* the water all the time, and they generally last a very > very very long time. I'm not suggesting you (or the tome) are wrong, I > would just like to learn a little more about the context and the actual > point that the book in question is making. Thanks. Mark, the book (and it's definitely a tome!) is on loan to a friend, so it will be a day or so before I can get hold of it. It is a classic in its field (circa 1978 copyright), and until I read it I would have had the same opinion you do -- based on the minimal corrosion visible **from the outside** on stainless. My post was specifically about "crevice corrosion," which occurs in covered areas of SS not exposed to oxygen (or, oxygenated sea water). Basically, because the exposed area of the SS becomes cathodic (due to exposure to oxygen), the covered area(s) become anodic, and hence are susceptible to crevice corrosion. This means that on areas under boltheads, areas enclosed in epoxy (etc.), the SS corrodes. In the book are many dramatic photos of drastically eroded surfaces from situations like the ones mentioned. When the covered area is small relative to the exposed area, then all the anodic activity is concentrated in a small space, leading at times to penetration of the covered surface, and possible failure of the fastener (etc.) at that location. What is insidious about this type of corrosion is that (as you say), the **visible** surfaces of the SS look good -- and they are -- but those areas not readily visible *may* not be. Please note that I am not saying SS is a poor choice for marine use. I am saying that in an application such as SS cable, with its substantial potential for crevice corrosion, regular replacement should be the norm, inasmuch as one can not readily check the "crevices" in cable non-destructively. I'll post the complete citation for the book when it is back in my hands. Believe me, it really opened my eyes to the complexity of corrosion in a marine environment. -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List - All postings copyright the author and not to be reproduced outside PaddleWise without author's permission Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Tue Apr 11 2000 - 17:37:03 PDT
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