How not to clean a fuel tank

[sbrumby]

I have an old friend who is always doing up old mopeds and small motorcycles, in fact his garage is full of them. He drops round to my place for me to do welding jobs for him. I had told him how I had cleaned out a rusty petrol tank by strapping it to a cement mixer with sand and gravel in. He in turn told a friend of his and they had a go about cleaning two tanks. The first one was ok, but the second one had been internally coated and this was coming off. Some of this shifted but some would not shift, they had some gravel but this was limestone chippings,this in turn did not do the job so the guy added some acid and sealed up the filler with a pice of rubber under the cap. They had not even started the mixer and a fizzing sound was noticed followed by a pop. The tank had gained a gallon in capacity and was buggered.

[Stuart]

Lol. In my yoof I once took some advice to get a dent out by sticking air into a tank. Despite sitting astride the thing it still blew up & out sideways & ended up looking like a pair of lungs!
I remember you saying the best way to clean a tank out prior to welding was with diesel.

[pietenpol2002]

Just this evening I threw a tank in the clothes dryer. Wasn't too bad on the inside but did show enough rust I didn't want to risk contamination to filters etc. A few shots of penetrating oil and a handful each of 1/4" nuts, lock washers and short bolts thrown in and then wrapped it in some old blankets. I had to add a bunch of my old jeans to fill up the dryer drum and then set it to tumble on the no-heat cycle. I should add that this was done with full disclosure to my wife who probably blessed it knowing that at least I wasn't in the kitchen conducting experiments in the microwave or oven. The inside of the tank looks great. I may have wash the blankets as they have a hint of penetrating oil, but I figure old jeans should smell that way.