That was one of my concerns with epoxy, 5200, etc. You need to know if it'll affect drinking water. That's why I suggested JB Weld from the outside. Simplest thing to try. If it doesn't work you've wasted $5. As for epoxying a plate inside, that will involve major (expensive) surgery. Still waiting to hear how big this tank is and where it's located. There was talk of baffles. Do we know there are baffles and how they're situated? Sure would like to see inside before spending big bucks only to have it corroded throughout the interior, maybe rotting through at another spot when you're done. I wouldn't go further than the JB without knowing the condition inside.