Cathodic Protection is a simple technical concept with profound implications for combating corrosion. As an electrochemical process, corrosion converts elemental metal or alloy to metal ions and electrons. By pumping electrons (in electrical current) in the correct direction, the corrosion reaction can be either slowed down or reversed completely. ISO 8044 defines cathodic protection as an “Electrochemical protection by decreasing the corrosion potential to a level at which the corrosion rate of the metal is significantly reduced”.
There are two commonly used cathodic protection technologies in corrosion prevention by utilising different energy sources:
a) Sacrificial Anode Cathodic Protection (SACP)
In SACP, an active metal or alloy (such as zinc, aluminium or magnesium) is introduced to generate the electrical current required for the corrosion protection. Anodes will be consumed gradually in this process.
b) Impressed Current Cathodic Protection (ICCP)
In ICCP, an external current is supplied through rectifier units.
Corrosion and Corrosion Control
an endless battle against nature
This means that any area of the protected structure within the electrolyte can be protected, whereas in the case of galvanizing, only areas very close to the zinc are protected.
With the development of this CP shielding phenomenon, impressed current from the CP system cannot access exposed metal under the exterior coating to protect the pipe surface from the consequences of an aggressive corrosive environment.
A Cathodic Protection Tester candidate should have entry level knowledge of galvanic and impressed current cathodic protection systems.