Finishing Idea
I did the whole tubbing deal two weeks ago, and for finishing I went over all my welds with Alex Plus which is a paintable silicone used in construction.Then I covered the metal with a thin layer of the goo and textured it by putting my finger tips on it then pulling straight back. This creates a really rough finish. When it was fully cured, I sprayed 3M Rubberized Undercoating all over the mess, several coats and I can hardly tell anything was done!
Epoxies might be a good choice for sealing too, but I work at a sheet metal shop and we had an entire self of Alex so....:homer: