Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Am certain it has been contaminated by oil or similar, which has stuck on there right through the sanding process.

When i repaint, i prefere to sand or blast to bare metal, wash with acetone or thinner to degrease, and then topcoat straight on there, and never have experienced anything like this on my toys.

I have however used grease to mask old tractorparts and machinery quite often, and the result looks exactly like yours...with the only difference that i aim to be able to peel off the paint in those areas.