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Old 25 January 2007, 11:32   #1
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Rib knife (non rusting)

I have a s/steel knive that is kept on the rib in its holder, but it rusts!!

Although it is s/steel there are different grades, many of which apparently tarnish and rust in a salt water environment.

I want to replace it with one that i can keep on the rib at all times for easy access and it won't rust. I understand that it needs to be of a surgical s/steel grade to ensure total rust proofing.

Is anyone aware of such a knife, how much and where i can get it from?

Cheers
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Old 25 January 2007, 11:36   #2
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Try titanium-it's not as expensive as you'd think and it won't rust.
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Old 25 January 2007, 11:43   #3
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Quote:
Originally Posted by ChrisB123 View Post
Although it is s/steel there are different grades, many of which apparently tarnish and rust in a salt water environment.
Generally speak A2 grade (automotive - type 304) doesn't have good salt water properties. However A4 grade (marine - type 316) is designed for purposes such as deck fittings onboard boat and is more more resistant.

Hope this helps

Andrew
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Old 25 January 2007, 11:45   #4
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Problem you have is that the higher the carbon content the better edge on the knife. Of course this means that the stainless will rust easier - so you can either have a knife that will never rust but has a crap edge or one that you can sharpen like a razor but will be covered in spots!!!
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Old 25 January 2007, 11:48   #5
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Try a good quality "Kitchen Devil" type knife. The blade is ideally suited to cutting wet rope, its guranteed (they wont know it lives on a boat) it's cheap to replace and most can be modified to make a blunt point. If you do wish to make it further resistant to rust or staining coat it thinly in divers silicone grease.

Titanium is an excellent material, however as a diver there's a never ending number of knives that get put away in Davy Jones's locker, it is unusual to get back a knife of the some quality as the one you lost...weird man!
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Old 25 January 2007, 12:06   #6
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Wikipedia is your friend:

http://en.wikipedia.org/wiki/AISI_steel_grades

or

http://en.wikipedia.org/wiki/Stainle...tainless_steel

or

http://www.bssa.org.uk/nsindex.htm

Cheers, WMM
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Old 25 January 2007, 12:23   #7
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Originally Posted by ChrisB123 View Post
I have a s/steel knive that is kept on the rib in its holder, but it rusts!!

I want to replace it with one that i can keep on the rib at all times for easy access and it won't rust. I understand that it needs to be of a surgical s/steel grade to ensure total rust proofing.

Is anyone aware of such a knife, how much and where i can get it from?

Cheers
Surgical grade does not mean it won't rust.

I don't think that any grade of SS is completely rust-proof; some are more rust resistant than others, though.

The best procedure I've come up with is to keep a coating of silicone grease on all exposed metal surfaces on the knife. A handle that can be disassembled helps here, as you can coat the entire piece of metal. The grease lasts longer than oil does. Use a grease certified for incidental food contact, and you're safe consuming the evidence of being attacked by that rampaging salami.

I've got a Underwater Kinetics dive knife that has been on my gear for years with no discernible rust problems. I think it's made from 420 SS. Their new ones are some proprietary SS blend called Hydralloy.

I dislike the titanium knives because they're too light. I like the heft of steel, as it makes it feel like I've actually got something in my hand.

jky
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Old 25 January 2007, 12:33   #8
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Titanium alloys can only be brought to Rockwell hardness In the mid 40s and do not hold their edge very well. Any steel alloy that provides a good edge will be subject to corrosion if kept continuously in a saltwater environment. Rather than keeping the knife on your boat, keep it on your person (lifejacket, belt OR both). That way you can rinse it off in fresh water dry it at the end of day. The blade can also be given a light coat of chapstick OR vaseline to help protect it from the elements.
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Old 25 January 2007, 12:49   #9
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The only option not mentioned are the new ceramic blades. They are VERY sharp and are reported to be durable. I only mention this because it was the only option not discussed.

My own choice is for a high carbon stainless that is easy to sharpen on my ceramic sharpener, is rust resistant and gets a bath in WD 40 from time to time. Other than very slight discoloring on the blade, it remains good as new in extreme salt conditions.
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Old 25 January 2007, 12:56   #10
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Try titanium-it's not as expensive as you'd think and it won't rust.
I'm with Matt, and my titanium diving knife holds a very sharp cutting edge wonderfully.
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