Mapei provides a range of solutions for galvanic cathodic protection against steel corrosion in reinforced concrete. They consist of Mapeshield I, Mapeshield S and Mapeshield E 25, which are quick and easy to install, do not require external energy source and are maintenance free.
These galvanic cathodic protection systems utilise Mapeshield reactive anodes, which form a galvanic cell with the steel and thus become passive due to the difference in potential generated between the two metals once they are connected.
The anodes are made from zinc, which is considered less noble than steel. They will be gradually corroded over the years and guarantee that the structure is protected from corrosion for a long time - up to 40 years for new structures and up to 20 years for repaired structures.
The Mapeshield systems can be used in many areas, including prefabricated reinforced concrete structures; beams and columns; floor slabs in raised carparks; front edges of balconies; concrete floors; piles, abutments, friezes, kerbs and floor slabs on bridges and viaducts; general reinforced structures, particularly those exposed to aggressive environments such as the sea; and beams, pillars, piles and steel tanks.
These pure zinc anodes with a coating of special conductive paste are designed for use on rebar in concrete. The system is well suited to protecting reinforcement rods against corrosion in both new structures and structures that require repair work.
Mapeshield I must be attached to the reinforcement rods before repairing the structure with mortar from the Mapegrout range or before casting the concrete on new structures.
The system is made up of a multi-layered zinc core with a large surface area, covered with a special conductive paste that keeps the system active over the years. After connecting Mapeshield I to the reinforcement rods with metallic stays, a difference in potential is created between the steel and the zinc, which stops corrosion and impedes its formation, even if the surrounding environment is aggressive.
Mapeshield I is available in two different lengths and four different masses, making it suitable for various structures. The surface that the anode is capable of protecting depends on its size (the bigger the anode, the larger the area it protects) while the mass, which is proportional to the amount of metal it contains, effects its duration.
Mapeshield I is compliant with the EN 12696 European standard ‘Cathodic protection of steel in concrete’.
These self-adhesive zinc plates can be applied directly on the external surface of metal structures that are exposed to atmospheric conditions.
When Mapeshield S is applied on a metallic structure, it forms an electrical interface between the surface to be protected and the zinc, thus transforming it into a galvanic anode that protects the structure from corrosion, even if the surrounding atmosphere is aggressive.
Mapeshield S is available in 50-m-long rolls at a width of 100, 200 or 300 mm. The zinc plate must be applied on the entire surface of the structure that requires protection. Once the plate has been applied, no other operations need to be carried out because contact with the structure is guaranteed by the adhesive.
Mapeshield S conforms to the UNI 10781 standard ‘Requirements of self-adhesive zinc tape, application methods and checking the dressing coat’.
Mapeshield E 25
These self-adhesive zinc plates can be applied directly on the external surface of concrete. To ensure the system is active, it must be connected to the reinforcement rods with a simple metal cable.
Once Mapeshield E 25 is connected, a difference in potential is created between the steel and the zinc, which then stops corrosion and impedes its formation even if the surrounding environment is aggressive.
The degree of protection depends on the density of the reinforcement in the structure. On heavily reinforced structures, Mapeshield E 25 must be applied on all the surface requiring protection. If the density of the reinforcement is low, the distance between the plates may be increased up to a maximum of 50 cm.
Mapeshield E 25 is also compliant with the EN 12696 European standard ‘Cathodic protection of steel in concrete.