Bonding and Grounding:

To prevent a spark from discharge of static electricity in during flammable liquid filling operations, the wire bond should be given among the storage holder and the container being filled, unless a metallic path among the container is or else present.

Above-ground tanks used for storage of flammable liquids do not have to be grounded unless that is on concrete or on nonconductive supports. The Ground wires should be uninsulated so they might be simply inspected for mechanical damage and should never be painted.  Below figure describes grounding above-ground storage tanks.

Bonding and Grounding