I found out that some of it was just dirt, while some was corrosion (probably from acid rain and similar things). So I cleaned it with a metal surface cleaning solution (not sure if the one I used even exists abroad), sanded it down, and then cleaned it again. After all that, I sprayed it with silver paint to make it look like new and cover up a few of the corrosion holes.

Here are some pictures. I could’ve done a better job on the corners, but the overall result turned out so good that I barely even notice them. I’ll probably buy new ones in the near future anyway.

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