Impressed Current Systems provide the same electric current as galvanic anodes by the discharge of D.C. current from a relatively inert anode energised from an external D.C. power source such as a transformer rectifier or thermo electric generator. Impressed current system anodes include materials such as silicon iron, platinized precious metals, lead alloys and graphite.
Effective cathodic protection guarantees corrosion free existence. Providing the structure is maintained at a potential of –0.8 volts (or more negative) no loss of metal will occur at all during the life of the structure. As cathodic protection can be renewed or added during the life of the structure, the maintenance of the desired potential is readily achievable. The efficacy of the system can be monitored by a simple electrical measurement.
Cathodic Protection, apart from overcoming the more ‘normal’ causes of corrosion, may be used to counter accelerated corrosion resulting from contact between different metals, from impingement by high velocity water, from the effects of sulphate reducing bacteria and from the effects of stray D.C. currents.