DIY & Home Improvement

DTM (direct to metal) paints bond very nicely, as do etching primers.

Wet sand it with at least 600 grit to break the surface. The acid based primers work nicely, it isn't necessary to sand much at all - sanding until it looks like you've sanded the whole thing is way too much work. Use a finer grit after the primer, wet sanding again.

The reason for wet sanding is because the sandpaper stops working almost immediately when dry - it clogs. Because it is hard to find open coat paper in local stores just put a few drops of dish soap in the water.