Looking at the engine for my junior fueler, I noticed this on the front cover...it's corrosion/rust! I didn't put it there (obviously, the cover would be aluminum, so, why would I? ). I sprayed the part with Testors metalizer, many years ago. I'm not sure what the yellow is, but, the reddish-brown is rust. Therefore, I have concluded that some of the pigment was iron. Anybody ever seen this, before?