I have a moble home Rheem water heater.72-40-2 RH1004273925 240/209 volts AC only. We did maintenance release because we were getting no hotwater and breaker kept tripping. We noticed small amount of rust near bottom thermostat. After the release we reset and it automatically tripped the breaker what could be the problem? Thanks for any help

Sounds like you have a dead short either in the elements or the wiring. Also check the thermostats. If they're sending power to both elements at the same time that would trip the breaker. Good luck, Tom