I don't know why I never thought of this before.
Keith, that is brilliant. How did the result turn out? Any before and after photo?
Keith, I would be interested in how this worked out. What did you do after spraying the plugs? I use oven cleaner on greasy parts an it works great.
Lye based oven cleaner such as what you are using will strip cadmium and zinc plating. (I know from personal experience that it will strip zinc plating). If those are Champion A25, the oven cleaner can strip the zinc plating.
I don't know if it will strip the oxidized/blued finish on Champion X, Champion 25 and the modern Motorcrafts, etc.
Won't hurt chrome plating.