I have had a lot of the parts plated. Most of them came back from the plater, some of the windscreen wiper parts didn't. They appeared to be some kind of aluminium alloy and dissolved in the prepping solution. The parts that came back look brand spanking new.

They're plated clear zinc, the plater calls it "blue", as it has a blue haze. The preparation of the parts shows through the zinc plating, as can be seen in below picture.

Blasted parts have a nice finish and the smoother surfaces are very shiny.