Have to credit my wife for this one. Get an used gas cloths drier. Gas because then you won’t have to monkey with the electric coils.You can easily get one for free. Take everything off the tank . Use an old fuel cap, housing, etc and make gaskets to seal the tank. Put a couple pounds of drywall screws in the tank. Next you can add WD-40, soap and water,or whatever cleaner makes sense depending on what is in the tank. Pack the sealed tank with moving blankets or tarps to keep it in the center of the drum and turn it on. The drier will tumble out any dirt, rust, scale or residue leaving a 100% clean tank. No shaking. No Evaporust . No electrolosis. Used it on dozens of tanks. If there any pinholes in the tank, removing the scale will reveal them. You may have to reposition the tank to bring the screws to bear on different sides. Usually takes about an hour or two, depending on how bad the tank is.
