Coffee = Stainless Patina?

O

Omega Leather Works

Joined
Jun 13, 2007
Messages
7,743
So I got to looking at a spoon that I keep in my coffee grounds 24/7. It's made of SS, granted it's cheap SS, and but the thing has turned very dark over a period of two or more years.

I tried to get a pic but it didn't turn out very well.

IMAG0331.jpg


My question (obviously) is... Is it possible that I might get a similar patina on one of my Spydercos or other knives? I would be fine with burying it for a year or two if it would work.

Which common SS are likely to patina in this way?

Thanks
 
Nice finding! Not sure if blade also will react the same, and not simply rust due to higher carbon content.

Maybe can try one with higher stainless properties? Can't recall which steel, but perhaps 440C?
 
coffee grounds are acidic, which is probably why a patina on stainless developed over time.
 
Strigamort said:
I would be fine with burying it for a year or two if it would work.
Click to expand...

I'm sorry but that statement is hilarious to me. Only a knife nut would say something like that.

Seriously though, I think the SS knife would rust before it would patina. Even putting a patina on carbon steel can cause some rust to form.
 
I would think baking soda and a scotchbrite would clean that spoon up no problem...
 
It could be oxidation; probably is, in fact. Looks similar to some stainless I've seen, which does tend to grey/darken over time, especially if exposed to acidic materials. My Dad uses a Victorinox SAK which has some discoloration like that on the blade; I'm pretty sure he's used it around some acidic materials. Another BF member posted recently, regarding another SAK that discolored similarly, after it was used to break up some Alka-Seltzer tablets (contains citric acid, I believe). I think even some 'passivated' stainless steels look like that. The passivation layer is oxide applied by chemical exposure (nitric or citric acid is often used), deliberately applied to some stainless steels used or intended for harsher/corrosive environments.

If exposed to the (acidic) coffee 24/7 as described in the OP, I'm not too surprised if it has oxidized a little bit. I might even try this myself; it looks interesting.


David
 
Last edited:
Curtis_Lowe said:
I'm sorry but that statement is hilarious to me. Only a knife nut would say something like that.

Seriously though, I think the SS knife would rust before it would patina. Even putting a patina on carbon steel can cause some rust to form.
Click to expand...

Haha I thought about it after you wrote that, and I guess you're right.

Regular cleaning doesn't remove it, but I haven't purposely tried to remove it either. Whatever the case may be I appreciate the input.

I think ill put a blade in there just to see. I'll get back to ya in a few... years. :p
 
Strigamort said:
Haha I thought about it after you wrote that, and I guess you're right.

Regular cleaning doesn't remove it, but I haven't purposely tried to remove it either. Whatever the case may be I appreciate the input.

I think ill put a blade in there just to see. I'll get back to ya in a few... years. :p
Click to expand...

Assuming it is oxide, it should polish off using something like Flitz/Simichrome, both of which will remove oxide from steels and other hardened metals. I don't think conventional cleaning will touch it, otherwise.


David
 
I wouldnt test it with a good knife.
Go buy a Frost knife (Frost, not Frost's) or an Appalachian Trail knife for under $5 to test it on.
 
get the grounds wet and very warm, it's an age old alternative to bluing firearms. Ever wonder why old muskets always seem to be brown but not rusted? Granted they were not stainless but some water and some heat will definitely accelerate the process.
 
I just realized you meant the metal was turning dark. I thought you meant it was getting dark and brown, like a coffee color.
 
You must log in or register to reply here.
Back
Top