probably too late but  my tankwas badly rusted and I cleaned it out with a  50/50 mix of water and muriatic acid.  Then I soldered on 14 patches on the outside of the tank over the holes then got a seal kit from my local jobber and lined the inside of the tank by rolling the tank around.  It worked.  The tank has been in use now for  1/12 years with no leaks.  (I did test it before installing it.