What is this under distributor cap

[murnan]

I removed the distributor cap (Merc 7.4L) to replace cap and rotor and noticed a blueish green buildup of a powdery substance on the round thing directly under the rotor, is this a cause for concern and what should I use to safely clean it up. Thank you for any help or advice its greatly appreciated.

 

[northern]

Green is usually copper oxidation. Looks like you have a lot of iron rust under the green. Assume from hot humid Florida weather.
Vinegar will remove copper oxidation.

 

[Loyd Dinneen]

That round thing is most likely a stator. From the looks of the distributor you need to do some rust control and put some corrision preventive there before it gets worst and leaves you stranded. Put dielectric grease under the module on the plate when reinstalling it.