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-----Reddish brown coating on hand tools
adv.
Quickstart:
Unfortunately, it's difficult to guess what a finish actually is based just on its appearance.
This thread mentions 'Corten' weathering steel which is designed to rust (but only to a limited extent), and 'black oxide' (which is the same thing as gun bluing), a black rust formed by immersion into very hot caustic solution with nitrites/nitrates.
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some readers skip abstract questions.
Q. What is Reddish brown coating on Allen keys or screw bits
Sandip SanagarOwners of a electroplating ind. - Nashik , Maharashtra, India
September 24, 2025
A. Hi Sandip
Sorry but I don't know. Please <send pics for posting> and additional descriptive info about your situation.
I suppose it's possible that cheap tools could be made of Corten weathering steel ⇦ huh? , but it doesn't seem like you could make self-weathering tool steels because they are heat treated high carbon steels.
Poor quality black oxide could be reddish brown, but I doubt that that is what your are interested in either.
Are you sure you're not just looking at lightly rusted items?
Luck & Regards,
Ted Mooney, P.E. RET
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