Most Stainless Steel? Not S30V!

Peter Atwood

Peter Atwood

Joined
Oct 26, 2000
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What steel has the most stainless properties? There must be one that is the most stain resistant of the knife steels. Which is it?

I was chagrined to discover a couple of pitted rust spots forming on a properly heat treated S30V folder blade this morning. The knife has been sitting unfinished in my shop for some time. All the windows are open and it has been quite humid so it would follow that rust could form. But a 440C blade that is also finished shows no sign of rusting at all. What's up with that?

And I know what some wiseacre will say...Just because it's stainless doesn't mean it won't rust. But obviously some are more resistant than others. Has any real testing been done to determine an answer to this?
 
Blade Magazine published results of am industry poll several months ago.

440C was first in stain resistance.

440A and BG42 tied for second.

AUS6 was next.

Probably subjective to some degree but a lot of experience in the ranking. Seems like any testing doesn't test for everything out there.

Don't feel too bad, made 50 steel anvils out of RR track last winter, etched my name on every one, went on vacation. Came back and found rust all over the etch on every one. Used the wrong neutralizer in the rush to finish!
 
Peter, this is hard to understand. I am looking at the Crucible
data sheet, and according to them, S30V is more stain resistant
than 440C. The method they used for the test is strange, I must say.
Looks like they used 5% salt solution and then applied voltage. Then
they called this "Average Pitting Potential." Huuummmm, I wonder if there is the scent of a RAT. Why didn't they just dunk it in the salt
and leave it for a while and see what happens?
 
I thought 440A was supposed to be more stain resistant than 440C, and 440B was somewhere in the middle?
 
Talonite Peter! :p :p :p

I am really impressed with S30V so far, but I know you weren't trying to start a debate about that...so back to your question (even though wandering off topic comes so easy to me :) ).

I think RWL-34 with a mirror polish is hard to beat for stain-resistance. Plus it just looks so COOL. I don't care much for mirror polishes anymore, but it's neat as heck in RWL-34. I have also had extremely good results with BG-42 in both stain resistance, edge holding and decent toughness.

440-C is very stain resistant, but I personally never cared that much for it. And the stuff I used was heat-treated by the master himself, Paul Bos. I am in NO WAY questioning Paul's work on the steel. I VERY SIMPLY think the properties of the newer steels just flat-out make them better for cutting.

However??? Some good examples of 440-C in the high end of cutlery would be Steven Rapp and Alex Daniels...just to name a couple. They build beautiful reproduction knives with it that look just as pretty (I'd bet more so) than the originals....plus they'll last till a quarter past Sunday.

I'm not sure when that is, but apparently it's supposed to mean a
L-O-N-G time :D
They're also not being used though.

Nick
 
Originally posted by kile
I thought 440A was supposed to be more stain resistant than 440C, and 440B was somewhere in the middle?
Click to expand...

This should generally be the case, all else being equal, for the simple reason that 440A has the "same" amount of overall chrome, but it has less carbon, which means less carbon available to bind up chrome in the form of chrome carbides. That means more "free chrome", and more free chrome means an improved ability to form chromium oxide, which is the surface oxidation layer that provides corrosion resistance, resistance to rust.

I wouldn't expect anything more than just normal "marketing" type advocacy from Crucible. There are a lot of ways to assess corrosion potential. They attempt to put their best foot forward, and in fact they sell 440C and 154CM, so if they say in their tests that S30V beats these two, well, it might, and it might be a bit of marketing puffery also, but nothing egregious.

Some argue, I think rightly, that a surface layer of iron oxide (red rust) is no big deal, especially where you can kind of buff or polish off the rust, but pitting corrosion, where metal is kind of eaten away, is a much bigger deal. (I don't pretend to understand the mechanisms that govern a surface layer vs. pitting type corrosion.) So Crucible may have been emphasizing pitting corrosion as a material property comparison.

From Crucible's data sheets, and from my hazy memory, in fact, the 420 series stainlesses beat the 440 series in corrosion resistance.

As usual, it's a matter of tradeoffs.
 
Mystery solved! At least I think it is....:) I spoke with Crucible's metalurgist this morning and we discussed my heat treat methods and other issues. I am reasonably certain that the problem lies with reusing my bead blasting media. I think that it is probably a source of contamination. I realized after closer examination that the rust was really only on the surface and that what was underneath was really not pitted at all. So I'm feeling MUCH better now.
 
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