Design Considerations
There are four primary questions to be answered when designing a cathodic protection system.
- How much current is necessary?
- What source of direct current should be used?
- How should installation be designed?
- How can effectiveness be measured?
Limitations of cathodic protection must be recognized during the design process. Cathodic protection will be effective only on metal surfaces in continual contact to the electrolyte. Above-ground structures will not be protected. The distribution of current to desired areas becomes difficult in congested or remote areas. Examples include multiple pipeline right-of-ways and storage tank bottoms.
Multiple variables should be considered during the design process. Two primary factors include the effectiveness of an external coating and resistivity of the electrolyte. The existence of a high quality coating minimizes current requirements of a structure and greatly influences the design. Electrolyte resistivity affects the choice between sacrificial and impressed current as well as the type of groundbed.
Other design factors include foreign system interference, power availability, maintenance requirements, and economics.
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