sourdough, Howdy;
If all fails try giving these folks a try, they go to the trailer and this is their
specialty, they do a "Power wash" and return the tank to as near as new as
possible. (usual disclaimer, I don't work for nor have I any interest in the company)
If I remember Texas is the home State for these folks, well, at least 3 folks that have a franchise ...
http://allprowaterflow.com/the-right-choice/
Best of luck
hank
__________________
Striving for a less complicated life since 1949 ...
Home: 2008 Cougar 278 RKS
T.V.: 2004 F-250 4X4, Level III BulletProofed , Detroit Tru-Track Differential (915A550)
Dog: 2006 Border Collie (Rascal) aka Maximum fur dispersal unit. (08/04/2006 - 12/16/2017) RIP.