Michael Daly" <michaeldaly_at_rogers.com> wrote: (In response to Steve at "ACKC" <aldercreek_at_qwest.net>:) > Stainless steel comes in quite a variety of grades. I am sure the grade of > SS in your knife is quite different from the grade used in deck hardware. >> But both the knife and the deck fittings rust. I've yet to discover an alloy of stainless that doesn't corrode. There aren't many stainless fittings on a sea kayak - a handful of nuts and bolts and a couple of deck U bolts maybe - these may not be considered critical if there's a thin layer of corrosion. Rudder cables are another story - swaged ends that have non-stainless crimps might corrode faster and could fail if not inspected regularly. I've noticed that some have aluminum bits and aluminum and steel are a famously bad combination. I've never seen this happen, so it's conjecture on my part at this point.>> Steve and Michael have it right: there is stainless and there is stainless. And, there is no grade that will not corrode ... eventually. Salt water, because of the chloride ions in it, is very aggressive towards iron-based alloys, owing to complexation of the chloride with ferrous (and then ferric) ion. The bottom line, however, might be whether the lifetime of the fitting, knife, or whatever, is "long enough." In full-size marine applications, it is good practice to pull a few fittings, especially fasteners, after four or five years, and inspect. Even stainless needs this sort of scrutiny because it is particularly susceptible to "crevice corrosion" in which the corrosion occurs in __hidden__ areas of low oxygen, where the lack of oxygen reduces the protective oxides of chromium and allows attack of the underlying iron in the alloy. (I know this is counter-intuitive; before anybody goes off on a rant, check out the term crevice corrosion. It is a well-documented problem for stainless, and well-studied.) This means that a little visible rust for through-hull fittings and deck hardware may be a __good__ sign, inasmuch as it may mean the stainless is still in an oxidized environment. Note: I said "may," and not "is certainly." YMMV when it comes to corrosion of stainless. I leave the problem of maintaining a shiny stainless knife in pristine condition to others. For me, I am content to know that the stainless I can't see, that holds my deck lines on, and allows my rudder to steer, is probably in good shape. -- Dave Kruger Astoria, OR longtime chemist *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Thanks Dave! Seems like I read that the more rust resistant SS is the softer/ weaker the alloy. es correcto? hence the poor edge holding capabilities of this *rust proof* knife. Just found this on http://divermag.com/archives/nov98/knives.html >>Blades can be made from a variety of metals but the most popular is stainless steel, either 304 or 420 grade of stainless steel alloy. The higher the number the lower the grade of stainless steel and the better the blade will keep an edge. A lower number means a higher grade of stainless and the more resistant it is to rust. Some of Underwater Kinetics line of Blue Tang and Remora knives are made of 316 grade stainless which offers a good compromise. A few manufacturers, such as Ocean Master, make knives from titanium which is light, very strong, keeps a good edge and is rustproof. The only drawback is that titanium is quite a bit more expensive than stainless steel. In any event, knives should always be rinsed thoroughly in fresh water after every dive and dried separate from the sheath. << steve *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
FWIW, titanium is also much more brittle than SS. Don't use titanium knifes as prybars or other titanium objects in situations where there may be quickly incurred stress loads. ;-) Dave G. - Poquoson Va paddler and old machinist At 07:31 AM 11/7/2002 -0800, Steve Scherrer wrote: >Thanks Dave! Seems like I read that the more rust resistant SS is the >softer/ weaker the alloy. es correcto? hence the poor edge holding >capabilities of this *rust proof* knife. Just found this on >http://divermag.com/archives/nov98/knives.html > >>Blades can be made from a variety of metals but the most popular is >stainless steel, either 304 or 420 grade of stainless steel alloy. The >higher the number the lower the grade of stainless steel and the better the >blade will keep an edge. A lower number means a higher grade of stainless >and the more resistant it is to rust. Some of Underwater Kinetics line of >Blue Tang and Remora knives are made of 316 grade stainless which offers a >good compromise. A few manufacturers, such as Ocean Master, make knives from >titanium which is light, very strong, keeps a good edge and is rustproof. >The only drawback is that titanium is quite a bit more expensive than >stainless steel. In any event, knives should always be rinsed thoroughly in >fresh water after every dive and dried separate from the sheath. << > > > >steve *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Couple URL's for those who want more on two of the common stainless alloys: 304 (less corrosion-resistant): http://www.assda.asn.au/304.html 316 (more corrosion-resistant; preferred for marine applications): http://www.assda.asn.au/316.html -- Dave Kruger Astoria, OR *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
G'day, Last night I bit the bullet and stopped rinsing the boat with fresh water. Its easy to dry off all the stainless fittings (including the rudder pedals) as we're in the middle of a drought and a very hot spell. Is there anything worth spraying on the fittings (especially the rudder pedals) that will help to protect against saltwater corrosion? All the best, PeterO (Australia) *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
At 10:51 PM 11/8/2002 +1100, PeterO wrote: >G'day, > >Last night I bit the bullet and stopped rinsing the boat with fresh water. >Its easy to dry off all the stainless fittings (including the rudder pedals) >as we're in the middle of a drought and a very hot spell. Is there anything >worth spraying on the fittings (especially the rudder pedals) that will help >to protect against saltwater corrosion? > >All the best, PeterO >(Australia) Peter, I use WD-40 spray. It displaces water and tends to leave an anti-corrosion film on metal. Use sparingly, it goes a long way. Dave G. Poquoson, Va. *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
Steve, I don't know about that weaker/softer = more rust-resistant generalization. I'm no metallurgist, so I'll have to plead ignorance. Too many variables, I think. Those URL's I posted might lead to better info on that. The generalization in the text you quote (that the higher the number, the lower the grade of SS) is wrong on one count, at least: 304 is not as corrosion-resistant as 316. I'm not familiar with 420 SS. Could be the 400 series is a very different series than the 300 series. I suspect if a person wants a truly rust-free knife, she has to get a titanium one. Bring lots of bucks! -- Dave Kruger Astoria, OR ----- Original Message ----- From: "Steve Scherrer" <flatpick_at_teleport.com> Subject: Re: [Paddlewise] Stainless Hardware (was: Cleaning fibreglass kayaks) > Thanks Dave! Seems like I read that the more rust resistant SS is the > softer/ weaker the alloy. es correcto? hence the poor edge holding > capabilities of this *rust proof* knife. Just found this on > http://divermag.com/archives/nov98/knives.html > >>Blades can be made from a variety of metals but the most popular is > stainless steel, either 304 or 420 grade of stainless steel alloy. The > higher the number the lower the grade of stainless steel and the better the > blade will keep an edge. A lower number means a higher grade of stainless > and the more resistant it is to rust. Some of Underwater Kinetics line of > Blue Tang and Remora knives are made of 316 grade stainless which offers a > good compromise. A few manufacturers, such as Ocean Master, make knives from > titanium which is light, very strong, keeps a good edge and is rustproof. > The only drawback is that titanium is quite a bit more expensive than > stainless steel. In any event, knives should always be rinsed thoroughly in > fresh water after every dive and dried separate from the sheath. << *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************
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