You can try citric acid from the bulk food store it looks like sugar might be more convenient as you mix it with water ,hot water in the sun may be better . I think t works a little better than vinegar ,I have seen someone derust by laying paper towel over a rusted dash and keeping it wet and it worked I guess like the gel idea .
I tried the jell on the rear of my frame. It worked but only to a point. This vinegar is o much better. I am sure there are other acids available and if I go bigger I will have to investigate because I looked up 30% vinegar in bulk. $850 for 55 gallons!!!
