BMW M52 engine build/ valves

Hi everyone,

i have a question. I’m rebuilding to a fairly standard spec a BMW M52B28. The engine has done a few miles and is very dirty inside! I am slowly getting there with the cleaning though. Now, my question is:

I have just started cleaning all the valves and hard carbon build up on the exhaust valves with a bench wire wheel. After I cleaned off the carbon on some of the valves I noticed some black staining on the valves, my worry is that this is plating that has started to come off, is this a thing?

Photo attached.

the marks did appear to be there under the carbon prior to wire wheeling.

thanks

Not hear of valves being plated. Maybe nitrided, an anti friction coating on the stem or a hardened tip.

Give them a polish.

Thanks for that,

have given them a good polish up now with scotchbrite and the marks are starting to fade. Must have been severely burnt on carbon I guess.