Anodized aluminum....the "coating" will not come off easily. I figured that out even trying aircraft aluminum "stripper". The only real way is to sand them out..... start out with the good old 220 and work your way up to 1200 or 1500. Then hit it with a good aluminum polish. In my case, I used White Diamond plate polish. It will take several days per bumper. And then you have the constant polish requirement to keep them looking like chrome.
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