[Capt. Bandaid]

That black you see on the surface of tool steel is probably Iron Oxide and maybe a bit of the carbon in the steel that was exposed when your sweat etched it. It will not harm it and, as has been said, probably protects it from further corrosion. However, I would keep the tools coated with a light oil or corrosion protection chemical.

[AlArchie]

There are at least two forms of Iron Oxide that I'm familiar with anyway.

Red Iron Oxide Fe2 O3.........common rust, and the same stuff that constitutes Jewelers Rouge. (2 iron molecules and 3 oxygen molecues)

Black Iron Oxide Fe3 O4.......that black stuff that is most likely the topic of this discussion. Some of that Rust Buster stuff, that works similar to the Naval Jelly corrosion remover, is a compound that converts the surface Red Iron Oxide to an Fe3 O4 Iron Oxide rust inhibitor.

There is also a particular steel alloy that forms a protective Iron Oxide layer when exposed to the elements that does not allow any further oxidation of the steel unless it is scratched. The the same oxidation process "heals" the scratch and the main beam is still protected against further decay. These steels are used in bridge and other structures that may be exposed to elemental damage.

Al

[BasketballJones]

Probably a dumb question but what is the black that gets on the tool when I strop at times? It always wipes off. Is that an oxide of something? It can't always be oil from the hands. I always leave the black on the strop, I know Chris Pye does that and I think that was a thread on this board.


Silver, I got a buddy who is diabetic that can tell his sugar count with in two by the smell and amount of his own perspiration. Something to do with keytones, amazing.

[Capt. Bandaid]

That blacks stuff on the strop, and you can get it even when you strop a bright tool, is carbon. Good tool steel has about 1% carbon in it to make the iron hard. When you strop it, you are polishing off a minute about of metal and that includes the carbon. It does no harm to the tool.

[Ashbys]

Chris,
It isn't anything to worry about. And it doesn't have to be associated with any major disorder. I have the same issue with steel, as a mater of fact I have been know to rust stainless steel , touch it an in a couple of day the black fingerprints will show.

I handel it in two ways, first I almost always use a bit of light oil on my hands, not to the point of being oily just enough to add a bit of protection, then when I am done with a tool , I wipe them down with a bit of 4 in one or wd-40.

The reaction is normal everyone does it to a degree, just some of us more than others. A slightly higher acid content is produce nothing more. I have worked in tool making for 30 years with it, I am just aware and take step to prevent the rusting.

Ash