Bronze-colored discoloration on blades?

[Svashtar]

On just a few khuks and one sword I have noticed an embedded bronze discoloration on a small section of each blade. Most just 1/2 to 3/4 of an inch long, and at the very edge of the blades. Definitely not rust, I would guess it's some by-product of the heat treating. They are in different areas of each blade, but all still fall within the hardened sweet spots.

Has anyone else ever seen any discoloration on any of their blades? Do you think it might polish out if buffed? The edges seem uniformly hard all along the edges, so I'm not worried about this affecting cutting ability; I'm just curious as to what it is and if it is in fact something that could develop into a problem.

Thanks for any info!

Regards,

Norm

 

[Josh Feltman]

Well, not sure if it's the same thing, but I had an 18" AK that had a small section of blade that developed a copper color after I etched the blade with vinegar. I scrubbed it off with a 3M green scrubbing pad. It didn't seem to affect the performance of the blade at all.

--Josh