why doea stainless rust

S

skidmark72

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Mar 31, 2013
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I have a benchmade with s30v s.s. it has some rust spots on the blade. But my spyderco h1's never do that. What cause some s.s. to rust and others will not. Thanks
 
Hello,

Stainless is kind of a misnomer. It is more like stain-resistant. All steels will rust, even "stainless" ones, its just that they are less prone to it. Keep it clean and oiled, out of corrosive environments, and you should not have to worry.
 
Stainless is not necessarily rustless. Rust is oxidation of iron...it is a chemical reaction. There are lots of chemicals around us and many of them will bring out the worst in your blade, so be responsible and take good care of it;)
 
As I understand it, the reason H1 doesn't rust is because it's technically not a steel, it's an alloy. It contains no carbon (it uses nitrogen instead).
 
Goosey said:
As I understand it, the reason H1 doesn't rust is because it's technically not a steel, it's an alloy. It contains no carbon (it uses nitrogen instead).
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Well..... Actually, ALL steels are an alloy. Steel is iron mixed with other elements to give specific properties. There is a category of steels called 'Alloy Steels' as apposed to 'Tool Steels', 'Carbon Steels', or 'Stainless Steels', but they are all alloys.

An alloy is a mixture or metallic solid solution composed of two or more elements.
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But you are right about the Nitrogen in H1 steel. It forms Nitrides in the steel rather than Carbides.


Manufacturer: Myodo Foundry

H-1 is a precipitation hardened steel, using Nitrogren to harden the steel instead of Carbon. This allows the steel to reach a hardness of RC 57-58, which is quite remarkable given the steel has very little carbon in it. Spyderco's H1 reported hits hardnesses of RC 65 on the edge according to Cliff Stamp.

With the introduction of H-1 knives, Cobalt Chromium alloy knives have mostly disappeared from the market. H-1 offers all the corrosion resistance of Cobalt Alloys without the added expense of material and production.

H-1 was introduced into the market by Benchmade in 2003, and quickly followed by Spyderco. Spyderco uses H1 extensively in it's SALT line of knives, which are designed for use in salt water.

Composition

C 0.15 Co - Cr 14-16 Mn 2 Mo 0.5-1.5 Ni 6-8 P 0.04 Si 3-4.5 S 0.03 W - N 0.1

Values are shown in percentages.
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Rust spots ?? Serious SS work requires the SS to be free of contaminents !! Machinig, grinding, filing etc of non-stainless will deposit iron on the SS.These can rust and the rust continue into the SS !! Serious work then requires separate tools etc for SS and carbon steel .For example a grinding wheel will pick up Carbon steel and contaminate the SS. In addition post operation proceedure is to "passivate" the SS. this is cleaning the SS by removing all foreign material with an acid.
 
Isn't H1 technically a ceramic?

And stainless isn't a misnomer. It literally is stain-less. If it was called stainproof that would be misleading. H1 won't stain under normal conditions unless exposed to certain chemicals. It also doesn't hold an edge very well, at least not the plain edge variety. In my experience it holds an edge more like AUS 4/6 which is barely a cutlery steel. But it has its place if rust is a concern. I have mine as a boat and swimming knife that you don't have to worry about. I end up at the gulf coast all the time and it comes in handy. Just doesn't stay sharp long. I've given 3 or 4 others away and sharpen them and they behave the same. A couple guys aren't knife guys and even they stopped carrying them because they don't stay sharp. One is a serrated model and it does seem to do a bit better. Just my experiences with it.
 
skidmark72 said:
I have a benchmade with s30v s.s. it has some rust spots on the blade. But my spyderco h1's never do that. What cause some s.s. to rust and others will not. Thanks
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The term "stainless" is not a binary term. It's a sliding scale.
Some steel alloys are more corrosion resistant than others.
  • Carbon actually forms a galvanic couple with iron. The more carbon in the alloy, the less "stainless" that alloy will be.
  • Chromium is the basis of the corrosion resistant properties of stainless steel. The more chromium in the alloy, the greater will be the corrosion resistance.
  • Other elements, such as molybdenum, enhance corrosion resistance.

Since steel alloys vary in composition, they have varying degrees of corrosion resistance.

Also, as has been touched on by others, the feature that makes "stainless alloys" stain less, is an oxide layer on the surface. Anything which causes imperfections in that layer, such as iron from milling tools, will cause the object to have corrosion issues. Once the protective layer is repaired, the corrosion resistance returns to that of the alloy.
 
"Stainless" Is a misleading word for all stainless steels to be in the same category when they all have different corrosion resistant properties. H1 being a true stainless steel, most should be called stain-less or stain resistant.
 
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Stainless rust because steel is a ferrous metal, meaning it contains Fe (iron) iron rust. H1 will not rust but it will corrode, rust is merely a form or type of corrosion. H1 will through chemical exposure corrode as will aluminum, titanium, etc. Titanium will not rust as it is a non-ferrous material. However, if you put in boiling sea water or certain very corrosive forms of acid it will corrode or begin to deteriorate through severe pitting. Titanium for example requires environments or chemical expsoure that would kill you anyway before it will corrode, so your safe on that end. It is immune to most acids but there are some very caustic acids that will hurt it, however those acids are so caustic humans can't even be around them without certain protective clothing and equipment. Not a place you would be using your titanium framelock, nor would you use it in boiling sea water, as well boiling water doesn't mix well with human flesh.

Hope that helps.
 
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