rust inside gas tank - 79 spit

[KEVIN EDDINS <eddinsk@NRISO.NOLA.NAVY.MIL>]

I recently found that i had a bit of water in the gas tank.  Upon removing it
all i found that i had a little visible surface rust.  
For about $50 - $60 i can have it cleaned at a radiator shop, but i was
hoping that there was some type of chemical that i could purchase and
do it myself.
If anyone knows about such a product, please let me know.

thanks,

Kevin