Here's what mine looked like under the heat wrap,. They were made from thin wall copper tubing, silver soldered together with a stainless steel flange. I would assume most that are is salt water will look the same once the cover is removed. Keep in mind these are unavailable now.
Often forgotten is the inside top of the tank, as almost always when you look through the access all you can see are the sides and bottom. When the tank is filled and your boat gets even a slight heel or bouncing around in rough weather, the water will sometimes self clean the top and deposits...
Did the affected tire wear on the inside or outside? It could possibly be another problem, such as a bent axle. An easy way to check toe in/out, is to measure inside on tires (side to side) and front and back .
A lot of problems also come from those who pay professionals for a service that aren't provided, this was the case on my boat. Educate yourself enough to identify where parts/service items are located.