I found this out by accident today. Glass beaded this intake and was getting ready to paint it and the road draft hole was full of sludge. I soaked it in my parts cleaner (old deep fryer filled with Cascade dishwashing detergent and hot water) and when I pulled it out it had a purplish look and some light corrosion. Kind of looked to me like weathered magnesium. Figured somebody might want to know this if they were trying to give some aluminum wheels a weathered look.