Tank liners are meant for leaking tanks. Using caustic / corrosive chemicals exasperates flash rusting. Although somewhat pricey (~25 bucks a gallon) , I use Metal rescue for ~24 hours, then a water flush. ANY bare, totally stripped clean, ferrous metal will develop oxidation overnight. Although I have not needed to do this on any tank I have rescued, spray some WD around inside to stop the oxidation process. (I have rescued some nasty tanks)
I also tumble it for a bit in my dryer.
Nothing beats bare metal inside the tank. Liners can become suspended in the different blends of fuels, and I personally remove any tank liners I run across. I hate having the same problems over and over.. like plugged carb jets. Filters will not catch the contamination.
Metal rescue will not harm paint. (NO, I do not work for them, I know what works) lol
Check out the dry coat at 5:51 in video.
An evapo-rust method from my limey brothers on the other side of the pond.