Case harden browned lockplate

[J.D.]

I am working on a cheap lock with a reeeeaaall soft plate. This lock is already browned, and to save several days work preparing a test piece, I am wondering if anyone knows what effect, if any, case hardening will have on the brown finish?

Thanks,
J.D.

[Stophel]

I'd say that you needed to clean the brown off just to get a proper job of case hardening.

[kedron]

I  do color case hardening.You need to remove the old finish and for the best colors you should polish the part.The less polish the more muted the colors are

[David Rase]

JD,  Once you bring the lock plate up to case hardening temperature you will lose the brown.  The brown should have no effect on making the plate hard.  Since you did not state you were interested in color, only functionality, I would just go for it and worry about finishing the plate after you have hardened it.
DMR 

[J.D.]

Thanks for everyone's replies.

I'm not necessarily interested in color case hardening, just hardening a very soft lock plate. I haven't contacted the owner, as yet, and was wondering what the heat and carbon would do to the brown finish on the plate, prior to making the suggestion.

Thanks,
J.D.

[Dphariss]

The plate will not be brown after being hardened.

Dan

[D. Taylor Sapergia]

Polish the plate well first.  It will be many times more difficult to polish when it has a glass hard surface, and any scratches will show up horribly.  After hardening, it will polish up again much easier.  Dan is right - the hard plate will resist oxidation.  It'll brown but you must be patient.

[J.D.]

Thanks everyone. I do appreciate you help.