dont gal it.
can only gal inside and out.
what you should do is:
sand blast
paint tank with 75 DFT microns Inorganic Zinc.
this paint is the paint idusties version of gal, works very well and you wont scratch it off easily it self repairs much like gal.
pro job only.
Tank should have class 2.5 blast.
coat with in 4 hours of blast,
Michael.
