My '67 GTR gas tank had quite a bit of rust, so I thought I'd give the white vinegar rust removal a try, and it works great! I had on hand both white distilled vinegar, and apple cider vinegar, and used both. I filled the tank to the rim, and let it soak for over a week, not because that was the reccomended time, but I had other things to do. Drained tank yesterday, and what a job the stuff did: sheets of rust and gunk came out, down to bare metal! Coated inside w/"RedKote" tank sealer, and now my tank is good to go. The vinegar treatment is much cheaper (and safer, by far) than nasty, toxic chemicals one could use for this job. Also did not have to agitate the tank, or add nuts/bolts to break loose the rust, but it woudn't hurt, of course. The used vinegar can be strained thru cheesecloth to by used again, but make sure you mark the container "not for human consumption"! This will be my go-to treatment, if I run accross any more rusty tanks in the future.
There are several youtube video's about this method; I also can list the step-by-step process I used, if anyone is interested.
