CATHODIC PROTECTION OF STEEL IN DEEP SEA:HYDROGEN EMBRITTLEMENT RISK AND CATHODIC PROTECTION CRITERIA

摘要

The exploitation of hydrocarbon reservoirs offshore West Africa will necessitate the application of cathodic protection to structures and equipment installed in deep waters.The design parameters given by the guidelines may need to be revised for projects offshore West Africa.Some results in the literature point out that hydrostatic pressure could have a detrimental effect both on hydrogen embrittlement and cathodic protection current demand.The present research programme aims to answer these questions.By using a specific high-pressure tank,which simulates deep-sea conditions,experimental procedures have been adapted from European recommendations for the conduct of such investigations.Ten steels of interest for their applications in deep-sea installations have been chosen.Six runs under 300 bar and 2 under atmospheric pressure were performed at Ifremer.No failure of steels with yield strength less than 1000 MPa is reported.This result highlights no specific effect of hydrostatic pressure on hydrogen embrittlement risk of tested steels.A higher cathodic protection current demand with pressure increase has been isolated.Nevertheless,CP criteria in deep sea are sensitive to the variability of environment,essentially water velocity.For reliable values,CP parameter in situ tests are recommended with deployment of data acquisition systems.