What is on my blade? (BM-943)

clanderson

clanderson

Joined
Dec 18, 2012
Messages
90
What is this disgusting herpes on my BM-943 blade?

I've had numerous S30V blades and I've never experienced pocket-sweat induced surface rust like this appears to be. I've had this thing less than 6mo. What gives?

(sorry about the poor focus)
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Probably is just sweat-induced rust-spotting. A friend of mine had the same issues with an S30V-bladed folder that he carried in his pocket in hot weather (central TX in the summer).

Sometimes the finish applied to the steel makes it more likely, as it can create more places in the surface (microscopically) for rust-making stuff to cling and collect. Bead-blasted finish is known for rusting issues, even on otherwise very 'stainless' steels, for example. This can explain why the same steel types from different makers behave differently with rust/corrosion, if they have different finishes on the steel.


David
 
Obsessed with Edges said:
Probably is just sweat-induced rust-spotting. A friend of mine had the same issues with an S30V-bladed folder that he carried in his pocket in hot weather (central TX in the summer).

Sometimes the finish applied to the steel makes it more likely, as it can create more places in the surface (microscopically) for rust-making stuff to cling and collect. Bead-blasted finish is known for rusting issues, even on otherwise very 'stainless' steels, for example. This can explain why the same steel types from different makers behave differently with rust/corrosion, if they have different finishes on the steel.


David
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Thanks David. You always come to my informational aid - appreciate your presence around here.

I have a fiberglass scratch brush - I suppose I'll just have to finesse that rust off of there and keep the blade lightly oiled.

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If you have some, or can get it, you might look into some Bar Keeper's Friend powder. Sometimes, mixing it with some water to make a paste, and then applying it directly to the spots (maybe with a Q-tip), then rinsing off after maybe ~30 seconds or so, is enough to make light rust-spotting disappear. Test the method on an inconspicuous spot first, to make sure it won't otherwise discolor or etch the steel. That can happen if you leave it in place on the steel for too long. Don't leave it longer than ~60 seconds at the most.


David
 
Obsessed with Edges said:
If you have some, or can get it, you might look into some Bar Keeper's Friend powder. Sometimes, mixing it with some water to make a paste, and then applying it directly to the spots (maybe with a Q-tip), then rinsing off after maybe ~30 seconds or so, is enough to make light rust-spotting disappear. Test the method on an inconspicuous spot first, to make sure it won't otherwise discolor or etch the steel. That can happen if you leave it in place on the steel for too long. Don't leave it longer than ~60 seconds at the most.


David
Click to expand...
That's a great idea - much less scary than my scratch brush heh. I also have a few bottles laying around. Thanks again!

Sent from my Nexus 6P using Tapatalk
 
Long time lurker, and can finally respond with some experience in stainless steel tooling and fermentation vessels.

The chromium oxides that lend stainless steels their protective layer can be penetrated by the surface being contaminated by chlorides (in sweat and laundry soaps) and other particles of carbon steel. Once the rust from the contaminants breaches the protective oxide layer, the iron in the blade or plate matrix itself will begin to rust as well.

In situations where this has happended, removing the surface rust and (re)passivating can be done in one step- using an oxalic acid-based cleanser (like Barkeeper's Friend) and a non-metallic scrubbing pad (like a green ScotchBrite), scouring the surface will remove dirt, oils and oxides. Towel-drying and leaving it to the (dry) air for a week will allow the blade to re-passivate itself itself and create a new chromium oxide layer.

We've recovered/restored many stainless-jacket surfaces that are situated in environments where carbon steel tools and tooling are co-located.
 
Dyn Blin said:
Long time lurker, and can finally respond with some experience in stainless steel tooling and fermentation vessels.

The chromium oxides that lend stainless steels their protective layer can be penetrated by the surface being contaminated by chlorides (in sweat and laundry soaps) and other particles of carbon steel. Once the rust from the contaminants breaches the protective oxide layer, the iron in the blade or plate matrix itself will begin to rust as well.

In situations where this has happended, removing the surface rust and (re)passivating can be done in one step- using an oxalic acid-based cleanser (like Barkeeper's Friend) and a non-metallic scrubbing pad (like a green ScotchBrite), scouring the surface will remove dirt, oils and oxides. Towel-drying and leaving it to the (dry) air for a week will allow the blade to re-passivate itself itself and create a new chromium oxide layer.

We've recovered/restored many stainless-jacket surfaces that are situated in environments where carbon steel tools and tooling are co-located.
Click to expand...

dyn - so if you were eventually going to apply something like tuff-glide, would you recommend letting it sit in air for a week first?
 
some tip's, wipe the blade from any fluids after use. if its particularly humid in your area, then apply an oil or wax to your blade to prevent rust spots further.
mineral oil or fluid film work great for me. there are many other solutions that will also work. put some on the blade, then wipe off, a very thin layer will be on it that you can barley see, this is good enough. re apply after cleaning or use depending on the use. make sure you use something that is food safe, but if you don't ingest stuff you cut or touch your blades that may not matter to you.
 
mhumphrey said:
dyn - so if you were eventually going to apply something like tuff-glide, would you recommend letting it sit in air for a week first?
Click to expand...

Yes. The oxide layer can't generate without exposure to oxygen. The blade needs to be clean and dry, or corrosion will occur on the unprotected surface before the oxide layer can form.

No damage would be done by using a treatment first, but doing so will prevent the oxide layer forming, and you'll not have the base protection inherent from stainless steel.

mhumphrey said:
dyn - so if you were eventually going to apply something like tuff-glide, would you recommend letting it sit in air for a week first?
Click to expand...
 
The oxides of metals can be very important for corrosion resistance .Once the oxides are removed rusting can happen. Proper stainless steel processing means never process stainless with tools used to process carbon steels . Serious stainless processing includes passivation treatment . Originally nitric acid was used to remove things like carbon steel on the surface but now citric acid is often used as it's more friendly for the environment. Other acids can also be used.
 
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