Help with stain on SS blade left in sheath

[Rev. Pete]

I tried "search" but it is giving me memory errors...

I have a new stainless steel knife that was inadvertently left in it's leather sheath for about 24-48 hours. When I took it out there was a brown stain about the size of a quarter on one part of the blade. I rubbed the blade down with CLP and the result is that there is a darker spot on the blade about the size of a dime. It doesn't look like the metal texture changed, it is just a darkening of the metal. The blade has a brushed finish. I'm a little puzzled here as the knife was shipped in the sheath and it was fine when it arrived. All I can think of is that the blade may have had a non-obvious protectant on it before it was shipped which then was wiped off. Or maybe there was some funky chemistry in the part of the sheath that touched the blade. The blade is described as "stainless steel". Ultimately I suppose I could involve the maker but I would really like to understand what might have happend and possibly fix it myself. I would appreciate any advice on what this dark area might be and how I could fix it. Thank you for your kind assistance.

 

[Matt Shade]

Chrome tanned leather is bad stuff for knives. You shouldn't store them in the sheath for long periods of time.
That said, 2 days for a stainless knife to do that just doesn't seem right. Most problems occur after long periods of time and effect all or most of the blade since the chemicals left in the leather are what is corrosive.
If the surface is discolored like that it will have to be polished out. You might be able to get it out with flitz or simichrome polish and not effect the overall finish of the knife too much. Or you may have to use some wet dry sandpaper and hand rub the blade to a new finish.
I would probably get in touch with the maker and see what they have to say about it. A stainless knife shouldn't rust that easily, so theres something going on there, and they may be willing to refinish the blade(which they can do a lot easier than you since they did it in the first place)If its something to do with the sheath, they should correct that too. You should be able to leave a knife in the sheath for however long you might be carrying it. Two days on your belt without a chance to wipe it down shouldn't be asking all that much.