Impressed current cathodic protection of reinforced concrete in ATEX-zones – Case study: concrete slab in an industrial building

Electrochemical repair by means of impressed current cathodic protection (ICCP) was adopted as a repair strategy for a reinforced concrete slab, severely damaged by chloride induced reinforcement corrosion. Since the slab is located within an ATEX-zone (i.e. a zone with a potentially explosive atmosphere), strict safety regulations regarding the maximum current output through the cables had to be taken into account in the design of the ICCP system. Therefore, the anode in the zones of the CP system was subdivided into small fields (subzones), each individually connected to the power supply and provided with an electrical fuse in the circuit in order to avoid exceedance of the maximum allowed current. Performance assessment of the ICCP system, based on 24-hour depolarization measurements at regular time intervals, showed that complete protection of the steel reinforcement was obtained, according to the 100 mV depolarization criterium in the European standard EN ISO 12696, while the current output was kept well below safety limits. During a monitoring period of about one year, a decreasing required current density with time was observed, which was found to be 4 to 5 times lower than the adopted design value of 20 mA/m² at the start-up of the system and up to 10 times lower after 11 months of continuous application