The required cathodic protection current is supplied by sacrificial anode materials or by an impressed current system. Most metals in contact with an aqueous environment having a near neutral pH can be cothodically protected.
Cathodic protection is used to prevent or reduce corrosion rates. Corrosion is an electrochemical process resulting from the formation of cathodes and anodes at different positions on the metal surface. Cathodic protection works by connecting the reinforcement to another material that is anodic in relation to it. The reinforcement becomes a cathode and its corrosion is substantially reduced.
There are two systems: sacrificial anode and impressed current
In sacrificial anode systems, the material of the anode is more reactive than the metal in the structure, e.g. zinc or magnesium; the anode is consumed in preference to the reinforcement.
In impressed current systems, the anode material itself may be inert but is maintained in an anodic state relative to the structure by being connected to the correct pole of a direct current power supply. An outline of the process is shown in the Figure. The anode is distributed over the surface (either an inert metal mesh or a conductive coating) or many discrete anodes are fixed in drilled holes in the concrete.
It is usual to carry out a commissioning survey once the system has been activated to check that the reinforcement is achieving the required degree of polarisation. Often a permanent monitoring system is installed to check that the system is continuing to operate successfully.
Cathodic protection does not eliminate corrosion. It transfers corrosion from the structure under protection, to a known location where anodes are placed and could be replaced easily. Cathodic protection overrides the naturally occurring anodic areas of a structure, thus turning the structure under protection completely cathodic, which means it receives current from the surrounding electrolyte (for example, soils, water) and does not corrode. Cathodic protection is achieved by passing enough direct current electricity from an external source (a more powerful anode), which could be a galvanic anode or an impressed current anode.
Incospec’s cathodic protection department is able to provide Cathodic Protection monitoring services, including fault finding and rectification, auditing of installed systems and cathodic protection contractors, design of sacrificial and impressed current systems plus installation of small sacrificial systems.
The current Indonesian Standards require ongoing monitoring and documentation. Cathpro Indonesia is well qualified to provide this service.
We provide regular checkups, reports and analysis to ensure optimal operation of the system.
Cathodic Protection Indonesia has many successful case histories of protecting structures, both buried and immersed, and can give advice on present condition and state of corrosion allowing calculation of future life of assets.
The full range of anodes for both sacrificial and impressed current systems are available from Cathpro Indonesia, including:
Zinc
Aluminium
Magnesium
Silicon iron
Mixed metals
Further Information
Please contact us for more details on the range of Cathodic Protection services we offer.
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