Cathodic Protection

Cathodic protection is used to control the corrosion of a metal surface by creating a current flow from the cathodic protection system to the structure. There are two basic methods; Galvanic and Impressed Current. In a galvanic cathodic protection system, the anodes connected to the structure requiring protection have a natural potential that is more negative than the structure’s. When the anodes are connected, a current flows from the anode (which is at a more negative potential) to the structure (which is at a less negative potential) in a DC circuit. OPERA has been used extensively to analyse this type of behaviour, primarily in the marine marketplace for corrosion protection of ships and boats.

Applications:

  • Ship hulls
  • Pipelines
  • Steel in concrete
  • Heat Exchangers
  • Marine piles and walls

For a typical marine galvanic CP analysis, Opera requires a model of the exterior surface of the vessel including
– Impressed current anodes
– Sacrificial anodes
– Painted and unprotected areas

The volume of sea and sea-bed surrounding vessel meshed with finite elements and material conductivity is specified.

Current density in sea for +500 A impressed current

Current density in sea for +500 A impressed current

Opera’s results post-processing allows for the interrogation of many useful results, including:
– Potential distribution on vessel, showing the effectiveness of CP system.
– Electric field distribution anywhere in modelled volume of sea and sea-bed
– Current density distribution anywhere in modelled volume of sea and sea-bed
– Resultant magnetic field from currents flowing in sea and sea-bed