G’day John, yep it’ll clean it out perfectly. If there is any fuel varnish inside the tank use a strong degreaser first (the one that came with my tank liner kit had to be mixed with boiling water, but worked really well) then dry it with a heat gun/hair dryer before filling it with phosphoric acid at around 10:1 water/acid ratio.
Try not to spill any on the tank, it won’t hurt it if you wash it off immediately, but might stain the paint if you leave it on. You can swish it around for an hour or so, drain it into a bucket and check to see how it’s looking, if not good enough, tip it back in again and keep swishing it around until you’re happy with it. When you’ve finished, tip it all into a sealed bucket or tub, and keep using it indefinitely. It’s great for fenders, headers, entire exhaust systems, etc etc. if it’s chrome, and not flaking off, it’ll make it look great.
Make sure you rinse everything with clean water or else you’ll have a cloudy layer of phosphorus over it. In the case of rims and pipes with slight pitting, a nylon or stainless steel scouring pad soaked in the PA will get all the crap off. If you can find my Redneck K2 Bitsa thread from 2017 or my Swamp Rat K2 build from 2019 you’ll see some before and after pics.