I recently removed the footrest and hind section of my pontoon frame and noticed rust on the ends of each of these pieces. Obviously, they painted the exterior of the frame but probably not the interior, this will probably not cause any problems for most of us. However, I happen to have a sample of a metal sealer so I soaked a piece of polyfoam with the product and swabbed in the interior of the frame tubes.

The rust was not extensive this was likely overkill, but that's the way I am sometimes.