I got a 2m length of tin a while back for £4 IIRC. The surface rust after 1 month was crazy, but it lasted me the year I ran it until I swapped to stainless.
I managed to repair a metal water pipe with arc a while back - so it is possible on thin metal, you just have to be pretty delicate - you can't let a pool build up properly, you have to build it up over and over - its slow and tedious, looks crap, but will work.