Cleaning dirty used stainless tanks?

[cray54]

I have a couple custom stainless tanks that have been outside for several years (turned on their side and used for wood storage). I'd like to properly clean them, but I need to use something more than just hot water. Further, I will be patching some holes and would like to know the appropriate procedure for cleaning after completing welds.

Thanks,
Chris

[maplefrank]

i would scrub with Shakee's Basic H

[arcticmaple8]

phosporic or nitric acid, same acid used to clean pipelines on dairy farms