Method and apparatus for cathodic protection of steel in a concrete structure located in an ionically conductive liquid

A method of cathodic protection of a steel reinforcement in a concrete structure located in an ionically conductive medium so that a first part of the concrete structure is in contact with the medium below a surface of the medium and a second part of the concrete structure, continuous with the first part, is above the surface of the medium, the concrete structure having the steel reinforcement in both the first part and the second part, the method comprising:

• providing a covering layer arranged to cover at least part of at least one outer surface of the concrete structure so that an inside surface of the covering layer is located adjacent said at least one outer surface;
• providing an inner anode of a sacrificial material for generating a galvanic current to the steel reinforcement, the inner anode being arranged so as to be positioned between the inside surface of the covering material and said at least one outer surface of the concrete structure;
• providing a bulk anode of a sacrificial material for generating a galvanic current to the steel reinforcement in the concrete structure, the bulk anode being arranged so as to be positioned outside the covering layer and below the surface of the medium;
• attaching the covering layer to the concrete structure;
• and providing electrical connections between the inner anode and the steel reinforcement and between the bulk anode and the steel reinforcement such that an ionic current flows between the inner and bulk anodes and the steel reinforcement tending to inhibit corrosion thereof;
• wherein the bulk anode comprises aluminum.