refinishing aluminum rub rail
I''d say use a clear epoxy paint or even varnish, though anything ''painted'' on is going to require periodic upkeep because it will chip off.
Having something as large as that anodized would be expensive, but it can be done at home if you have the room.
either dig a trench in the yard, or build a trough with 1x lumber and line it with plastic sheeting, build it to be able to cover the entire part, fill with your chosen solution and hook up the anodizing leads. sealing afterwards can be done with a steam gun, or hook up a pump to circulate very hot water from a boiler/water heater