Question about carbon steel, possible corrosion

[slight_return]

Hi all,
I bought a kellem wolverine about a year ago. Haven't had a chance to use it in the last couple of months, so it has been sitting in its leather sheath. When I took it out I noticed it has developed quite a few "black freckles" over the blade. I'm wondering if anyone knows what these are, if they need treating and, if so, how?
Thanks.
Here's a pic:
http://www.flickr.com/photos/66882000@N06/6087495200/

 

[cowboy]

Ayup mate, unfortunately this is the down side of having a carbon blade.. iv got a few with the same problem. But a top tip to get the freckles off is baking soda and a tooth brush.. sounds strange i no! and then if your not using the knife either add a drop of oil onto the blade or you can smear wax on it that stops any corrosion!!

Check it out on youtube! i was a few videos on there...

Hope this helps pal,

ATB

 

[John Fenna]

Patination of the blade (wrapping it overnight in vinegar soaked tissue) will help protect against corrosion....

 

[Stew]

Yep, it's corrosion but it won't be a problem as you use it and sharpen it.

some alternatives to vinegar for forced patina:
- english mustard (not the best I've used)
- tabasco sauce
- burger relish

A thin layer is best, or even just dotted on. Play about - it's actually a bit fun!

 

[Retired Member southey]

or chop up a few onions for a lovely oil effect

 

[slight_return]

Thanks all for the replies. I'm thinking of forcing a patina, however just need to clarify something. Does anyone know whether this black specking over the blade is the beginning of a naturally occurring patina, or whether it is harmful rusting? If it's patina, presumably I can force a patina over the top of it, whereas if it's harmful rusting I'd prefer to remove it first. Thanks again for any advice.

 

[Retired Member southey]

have you tried giving it a wash with a green type sink sponge, the ones with the scouring pad on, it looks to me like very light surface oxidation, nothing to be overly worried about, it might show through if you were going for any kind of patter but other wise i wouldn't worry,

 

[Stew]

Yep, it's just little bits of patina. No harm in it.

 

[ged]

If like me you're not a fan of patination I'd suggest polishing it with something like Autosol. If the spots are deep pits that isn't going to solve the problem easily and you might need to look at other ideas.

It's generally considered a bad idea to leave any knife in its sheath for long periods, especially a carbon steel blade and especially a leather sheath, but stainless blades can pit even more badly than carbon steel. Before putting them away for any length of time I spray all my blades with WD40 or 3-in-1 oil, and wipe the oil all over the exposed metal parts. For long term storage I'll wrap them in an oily cloth in turn wrapped in a polythene bag or something like that.

 

[shaggystu]

if that was mine i'd just give it a quick strop with some autosol on a bit of leather, it'll come up like new. in fact, that's exactly what i do with my kellam wolverine, it's all it ever needs

stuart

 

[ged]

Thanks all for the replies. I'm thinking of forcing a patina, however just need to clarify something. Does anyone know whether this black specking over the blade is the beginning of a naturally occurring patina, or whether it is harmful rusting? If it's patina, presumably I can force a patina over the top of it, whereas if it's harmful rusting I'd prefer to remove it first. Thanks again for any advice.

Most likely it will be a bit of both, as both are formed in similar processes and you need reasonably controlled conditions to ensure that you get one rather than the other. Your conditions were probably pretty random.

The dark grey patina is magnetite, which is one of the iron oxides. It forms the black goo in your central heating system for example, because there isn't enough oxygen to make rust -- but it's well on the way. Magnetite is a fairly hard coating which sticks reasonably well to the steel surface if it's kept dry enough. It's also seen on things like rolled steel bar, joists and plate, where it's called mill scale. It doesn't protect the steel as well as alulminium's oxide protects aluminium or chromium's oxides protect the stainless steels, but being hard, well-fixed to the surface and fairly impermeable it does help a little.

The red stuff (rust) is a different iron oxide and it's hydrated (meaning there's water chemically bound inside the rust). It's relatively crumbly, and it doesn't stick well to the steel surface so it flakes off leaving more clean steel surface exposed to attack.

You can convert one oxide to the other with some preparations. You can also do things like phosphating with e.g. Naval Jelly or various proprietary rust destroyers which can work well.

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

 

[shaggystu]

a few people have stated, quite correctly IMO, that leaving a knife in its sheath for long periods of time isn't a good idea. all i can say from personal experience of this knife is that storing it in the sheath doesn't seem to cause any problems at all, maybe it's because the sheath has a plastic liner, maybe it's because i've never stored it without using it for more than a few months, maybe it's the few drops of olive oil i put in the sheath when i first got it, whatever the reason, mine's always been fine.

as for patinating the blade, well that's fine as long as you're going to put a secondary bevel on there, at the moment with the scandi grind that the knife has as standard you'd be removing the patina when you sharpen the knife.

stuart

 

[Retired Member southey]

All mine live in there sheaths, unless the sheath gets wet then its dried an the knife returned to it, never have any issues of rust, but they do get used a fair bit,

 

[Stew]

All mine go in their sheaths too but then I don't worry about a rust too much, not that there ever is any.

 

[Retired Member southey]

Infact my new handles one all ready has an onion cutting oil like color to it

 

[Stew]

The only thing I find annoying about doing an onion patina is that you get that curve at the handle end of the blade.

 

[Retired Member southey]

what about blending the onion and dipping the blade in(first stopping the blender)

 

[mountainm]

what about blending the onion and dipping the blade in(first stopping the blender)

Can't you just chop a flat spot on each onion and kebab until the knife is covered.

 

[Stew]

what about blending the onion and dipping the blade in(first stopping the blender)

Smearing in burger relish is less effort.

 

[Retired Member southey]

or whittle the matching shape of the handle into the onion! hahaha nothing easy is worth it!