STUDY ON THE EFFICIENCY OF A COMBINED CATHODIC PROTECTION SYSTEM: MAGNESIUM SACRIFICIAL ANODE AND TITANIUM IMPRESSED CURRENT ANODE INSIDE DOMESTIC BOILER

In this work, the efficiency of a combined cathodic protection system composed by a sacrificial anode of magnesium and an impressed current anode of titanium, both installed inside a domestic boiler of 60L, was studied. The system was studied varying the specific conductivity of the water (50 µS/cm - 1000 µS/cm) and the temperature (20°C - 75°C). For assessing the cathodic protection efficiency, six localized probes were developed and located on the critical points of the boiler tank such as welded joints. These probes were able to verify the efficiency of the cathodic protection system through localized measurement of potentials of simulated defects placed on the internal walls of the tank. A monitoring workstation was set up to measure continuously the potentials in correspondence of the six probes, the heating element flange and the tank walls. The study showed that the protection system was able to protect all the metallic parts of the boiler in each experimental conditions. Furthermore, even an overprotection condition of the system, determining a possible hydrogen evolution was observed. In order to eliminate this issue and to guarantee a good management of the combined cathodic protection system, it could be helpful to decrease the current supplied by the impressed current anode.