Last night I reconditioned the 2 BMW allowys for the rear axle, and painted them gloss black to match the steels I had done earlier. I had been warned not to grit blast them, as it might be too powerful and open up the pores of the alloy, but found that by turning the blast pressure down to 25psi, I could remove the paint without damaging the alloy itself. I then went over them again with a sandblaster (actually pink aluminium oxide grit but very bery finely ground) and this left a nice smooth surface, but sufficiently keyed to accept paint easily. Anyways, here's the pictures:

Ok here they are before I started, one was painted black. I masked the centres of both, as they did not need painting. Just worth a mention that the tape is fibreglass tape, ordinary masking tape wouldn't be able to resist the blasting process.

Here they both are after a good 45 minutes of grit blasting, and a 10 minute sanding.

A close up of the inside of a wheel shows there is no damage to the surface of the alloy, just nice and ready for paint.

Back in the spray booth, primer applied.

Followed by gloss black. And what a pain in the neck they were to paint, all those different angles in the multispoke pattern. But I am really pleased with the result.