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Originally Posted by benoit454
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I used to polish aluminum for a company that did aluminum bumpers for 4X4, Ive attached a pic of the bully dog truck we did.
It sounds like you jumped too much between grit sizes, and also may be going too fine. When you polish aluminum, you want to use grits that are aggressive enough to get the scratches out, but not soo agressive that you are removing a lot of material. once you find the grit that removes the scratches you see, jump up by about 100 grit count and DA again. continue this until you are up around 800-1000 grit, then use white rouge on a buffer, then mothers aluminum polish. The scratches you are seeing is from your 400 grit that the 1500 could not get as deep as. As you sand it, you go from rougher to finer grit, slowly going from bigger scratches to smaller, to smaller, until you dont see individual scratches but a dull aluminum finish. this is the surface becoming completely uniform. Then when you hit it with the wheel it polishes up quickly and easily, and the mothers (or your fav other aluminum polish) to finalizes the shine. You will not have any of the hazy spots if done this way either, but a chrome look. We always used 160, then 220, 320, then 400 grit, sometimes 600 if polishing stainless steel just because its easier the get the scratches smaller with a DA than on the buffing wheel (stainless is a pain to polish and gets super hot). You have to make sure you seal it once you are happy with your results or it will oxidize and you will be doing this more than you want, as we learned the hard way on these big bumpers haha