Application of cathodic protection for controlling macrocell corrosion in chloride contaminated RC structures

• Theoretical basis of cathodic protection for macrocell corrosion is discussed.
• Macrocell corrosion under cathodic protection is numerically simulated.
• Cothodic protection current tends to flow into the more positive cathodes.
• Patch repairs containing sacrificial anodes inhibit ring-anode macrocell corrosion.

This paper examines the effect of macrocell corrosion on the current distribution in cathodic protection. The electrochemical corrosion process involved in typical chloride-induced steel corrosion is numerically simulated by employing the finite element method. The modeling results show that the protection current tends to flow into the more positive cathodes (passive zone) and reduces the galvanic macrocell current between the active and passive steel. Macrocell corrosion may also increase the non-uniformity of cathodic protection around the steel–concrete interface. Patch repairs containing zinc sacrificial anodes have been found to be rather effective in inhibiting the ring-anode macrocell corrosion effect around the substrate–patch interface.