Step 3: Prepare tank
Take of the top and bottom of the casing, then use a screwdriver or pry bar to open the crimp where the casing is joined together. This can also be done using a grinder fitted with a cutoff wheel, or a Sawzall and a very fine blade. If using these methods be careful not to cut too deep as the inner tank is about an inch below the casing.
Pull the casing off and remove the foam insulation below, by scraping with a putty knife if necessary.
Sand the tank down and use a wire brush until most of the rust is removed.
Paint tank with flat black metal paint. Rusty metal primer is recommended but optional.