By some chance I came across an article by 'the kneeslider' on how to remove rust from the inside of a petrol tank (gas tank for USA folk!) using electrolysis. Very interesting and simple.

Click here to go to the website.

Worth bookmarking for later use or passing on.

Although not mentioned in the article, you should fill the tank with water (or inert gas - don't ask!) to get rid of all the petrol fumes. Remove water, allow dry out and off you go...