I work in a foundry that manufactures nothing but boat parts. All the structural parts of the boat, the rudder and drive supports are made for salt water. Steel would be great, but it rusts and deteriorates. So, boat parts are made from either brass or manganese-bronze, which NEVER rust. Since salt water is much harsher an environment than fresh, all boats are suitable for fresh or salt. It's difficult to believe, but IF a boat sank, the drive shaft, the shaft supports, the rudder, and the through hull fittings would still be perfectly serviceable a thousand years later. They won't ever rust, cuz they aren't made of steel. (Drive shaft IS steel, but stainless steel.) Edit Edit I should have qualified my answer. I speak of boats up to about 150ft. We don't pour parts for larger craft- the largest we make is only about 400 lb. shaft supports, and the largest rudders are only about 6' long, exclusive of shaft. Even the screws, and nuts and bolts used on boats, are made from stainless steel. Heck, even the bells on boats are made from red brass, and then are made pretty by having the bell chromed. Even the bell will last a thousand years.
· 1 decade ago