I have re-anodized all the ones in my boat. I had to strip all the hardware to get ready to prep. Remove the anodize using sodium hydroxide and then buff out any discoloration using finer grades of scotchbrite. Anodize will not cover any blemishes. I then sent all the frames to an industrial anodizing company for anodizing. I would give you the name, but I was not pleased with their service and would not recommend them to anyone, but the results were good. It was a customer service issue only. Anyway, the frames did not look brand new, but not far from it and they were in pretty poor shape when I started. It cost me ~$300 for the entire project, plus sealer to reinstall the frames. It made a tremendous difference in the appearance. The hardest part was getting the old stainless screws out of the aluminum frames. Good luck!!Anyone got a good way of cleaning anodized aluminum porthole frames to bring back the new look? Or has anyone de-anodized them back to shiny aluminum, if so how did it come out looking?