I thought i should post this, 
http://www.yachtsurvey.com/fueltank.htm , it seems foaming fuel tanks in isn't a bright idea anymore. The following is from the site i just linked:
Fuel tanks don't corrode because they get wet; they                corrode because at some point something is in contact with the tank                that traps water between it and the tank. Like the original foam                that it was installed with. 
Aluminum is self-protecting,                so long as the surface gets adequate air exposure. Severe corrosion                is always caused by water plus a lack of oxygen. 
makes me wonder, does the coal tar epoxy help or hurt the new tank? 
