ABSTRACT:

The experience of the Total Group has been compiled in matters of Cathodic Protection (CP) of offshore structures and pipelines in order to draw conclusions from the cumulated field experience obtained for 40 years in various geographical areas. More especially, results of monitoring and underwater inspections have been studied to evaluate the performance of CP systems. After some initial difficulties due to not adapted designs or low-quality galvanic anodes, CP has been achieved in very good conditions, preventing corrosion and fatigue-corrosion failures. Protective potentials have been ensured with much lower current densities than values taken in calculations. Consequently, residual lifetime of anodes systems is generally much higher than initially foreseen, which often allows interesting prolongation of the platform life when needed. CP of offshore pipelines is very efficient. No corrosion has been encountered, which is not the case with buried onshore pipelines when coatings are disbonded. Coating breakdown factors taken for CP design have been very conservative, leading to actual lifetime much higher than the design value

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