Keep clean. One of our members had his tower re-finished,, on the boat. Looks like new. It still needs to be washed often.
Woody Wax is a popular option but it needs to be applied regularly and liberally in salty environments. The best solution is Capt. Ralph’s advice… keep it clean.
I was on a sportfish that used Vinyl wraps over the anodized aluminum. The warp was a few years old and still looked great and was really easy to clean.
The go to with all of the sportfish guys, is to put a coat of Collinite insulator wax on it. Lightly rub on, let dry, rub off, about every 3 months or so.
https://showboatcustomcoating.com/ I've used these guys & their product on 3 boats and they've been great. Previous boats tower was turning white in some areas and regardless of what product had been tried, the aluminum turned white in a day or so. At the time they told me they had done one that 8 years later was still shiny silver and that was also the case with mine that I later sold. Only been two years since current tower was done but it was shiny silver to begin with. Not cheap & a lot of work but IMO well worth it.