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ABOUT CATHODIC PROTECTION

THE CRITERION OF CATHODIC PROTECTION:

The true criterion for complete cathodic protection of a structure is the polarization of the cathodes on the structure to the open circuit potential of the most active anode on the structure. In practice, we use criteria defined by IR -FREE potential according to standards (e.g. NACE Standard SP0169; International Standard ISO 15589; EN 12954)

CATHODIC PROTECTION WITH IMPRESSED CURRENT AND TRANSFORMER RECTIFIER (ICCP)

This system of cathodic protection consists of CP transformer rectifier station, anode bed, cable connections and test points. By controlling the CP station output current, the pipeline is maintained at the necessary potential. CP station is designed for continuous operation. To check if the system works, test points are installed along the structure (pipeline etc.).

Fig. above – ICCP system for pipeline

Fig. above – ICCP system for complex structure

CATHODIC PROTECTION WITH GALVANIC ANODES

The structure is connected to the galvanic anode which has more negative potential and due to the difference in potential, the electrical circuit is formed which results in anode dissolution whereas the steel structure remains protected. The protectors are usually made of magnesium or zinc alloy. This system applies to shorter pipelines and reservoirs.

Fig. above – SACP system

CATHODIC PROTECTION OF REINFORCED CONCRETE STRUCTURES

Cathodic protection is the only way to arrest corrosion on steel reinforced concrete structures that have chloride contaminated concrete. The system consists of MMO anodes which are embedded in concrete, CP transformer rectifier, reference electrode and cable connections. Cathodic protection can be applied to old and damaged reinforced concrete structures, but also it can be mounted during the construction of new concrete.

MONITORING THE CORROSION

The system for monitoring corrosion consists of corrosion ER probe, reference electrode Cu/CuSO4, data logger and suitable software. The ON/OFF potential of cathodic protection, intensity and density of corrosion currents (AC and DC), alternate voltage on the pipeline and corrosion rate are measured. Measuring corrosion is an efficient way of establishing the efficiency of applied measures against the corrosion.

REMOTE CONTROL AND DATA MONITORING

The cathodic protection stations and test points can be upgraded by the system of remote monitoring and control. The connection could be based on GSM, GPRS or on the radio signal.

ECONOMICAL JUSTIFICATION

The maintenance costs are apparently reduced if corrosion detriments are avoided. Cathodic protection is solely a method, by which it is possible to protect already buried pipeline / tank, without excavation, sand blasting or the installation of new isolation. The use of cathodic protection is completely justified for new as well for old steel structures, as this system completely arrests any further corrosion and hereby exploitation period is extended for several decades.