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Galvanic cathodic protection of steel in concrete
The standard ISO 12696:“Cathodic Protection of steel in concrete” details the principles of CP and its application to steel in concrete. The purpose of cathodic protection of steel reinforced concrete is to suppress the corrosion process of steel in concrete by use of an applied current in structures that are supposed to be contaminated by carbonation and / or by chlorides during its useful life.
CP of steel reinforced concrete structures can be achieved by polarising the steel reinforcement with an external direct current (DC). For this purpose anodes are either surface mounted, painted on to or embedded in the concrete and connected to the positive pole of a DC power supply in the case of impressed current (ICCP), or directly connected to the steel reinforcement in the case of galvanic anodes.
For galvanic cathodic protection (GACP) the anode (typically zinc) provides the external current for CP. The liquids within the concrete pores (pore solution) function as an electrolyte and will permit ions to flow within the electric field created by the CP system. Sufficient corrosion protection is given if specific criteria for protection are met at representative points within the structure.
GACP systems, using galvanic anodes, have recognised advantages of simplicity and reliability, and have recently become available as a viable alternative to ICCP. Unlike ICCP, GACP systems require no extensive wiring or conduit, and no power supplies. Their inherent simplicity greatly reduces the need for ongoing monitoring and maintenance.