Aluminum forms a thick layer of oxidation that protects its finish. But, if that layer becomes damaged, it has to be buffed off and allowed to reform again. The layer is extremely hard and difficult to remove. It can be done with steel wool or wet sanding with a 320-400 grit paper. Follow it up with some white rouge buffing compound. One of the advantages of aluminum is that it is not a coating, no matter what happens to it, you can buff it back to shiny again. It just takes some work.

If you decide to get a pan chromed at a shop, don't take that Chinese pan in. Do yourself a favor and buy a good thick one from Milodon, buff it's coating off, and get that pan chromed. Milodon pans are much thicker than a cheapo pan and they magically carry an extra quart of oil even though the pan looks and fits the same as stock.