The black is 'engine black' and is high temperature paint. Not that the valve covers need them, but the original coating is undoubtably a polymer based paint. The original primer is an epoxy primer - two stage. One can't buy two stage expoxy primer in a rattle can. Why expoxy? Magnesium wants to oxidize and is porous. BMW valve covers are painted inside and out.
Paint process I used:
1. Used Mar-Hyde paint remover to remove all paint and coatings from the 'cover' only. I did not want to remove the paint from the 'cooling fins'. I used blue 3M painters tape to seal off the 'fins' from the paint remover.
2. Used a wire brush, finger nails, and a plastic scraper to remove the softened paint. It took time. It came off like skin after a bad sunburn.
3. Used steel wool to remove all traces, especially around the 'lip' and 'magnesium' text.
4. Sprayed the bare metal with primer. A filling primer.
5. Sprayed the cover black, using satin black engine paint. Removed tape before paint had dried hard.
6. taped off the section I wanted to paint 'bronze'. Sprayed the color. The first time it bubbled. I don't know why. I had to remove all paint and start over. Removed tape while paint was still tacky.
7. Cut strips of blue 3m painters tape to cover the 'fin' lines and applied the tape to the fins.
8. Painted the fins with the engine black. Removed the tape while paint was tacky.
9. Touched up areas along the fin line where paint remover had taken off the 'clear' coat using silver paint and a small brush.
...bolted covers on and rode it for 50 miles. Ahh the smell of baking paint!
I haven't ridden it on 200 mile ride yet so I can't say how this paint combination will hold up. It cost me about $30 in materials, $25 for a scarred valve cover, $90 for an unscarred valve cover.
I've added pictures of the left and right valve cover. The right side came out nearly perfect. The left side has one paint 'sag' - but it still looks better than 'blue'. I also swapped out the 'silver' spark plug covers for black ones. It just looked better to me.
I have not been able to use the Img or Quote features to include photos. How is this done?