Offshore oil- and gas-production environments provide severe challenges in
terms of materials selection and day-to-day operations. Several issues
encountered during commissioning of a North Sea platform and the remedial
actions are presented.
Corrosion protection of carbon-steel bolting by encapsulation was employed
to stop deterioration of an improperly applied anodic coating.
Iron contamination from debris generated during topside construction and
chlorides from the marine atmosphere provided the conditions necessary for
ferric chloride pitting corrosion of uncoated 316 stainless steel (SS), duplex
and super duplex SS, and 6% Mo SS pipework and vessels. Several offshore
cleaning/coating methods were evaluated, and a new procedure for cleaning was
identified that achieved the desired goal without removal of metal or affecting
the corrosion-resistant alloy's passive film integrity.
Insulated SS instrument tubing was susceptible to crevice corrosion and
chloride stress corrosion cracking (Cl-SCC) under wet insulation at the
temperatures generated by the heat tracing. Solutions were suggested to
minimize such forms of corrosion.
Coatings exceeding the manufacturer's recommended thickness had been applied
to several high-temperature vessels and to pipework to prevent SCC as well as
ferric chloride pitting. The potential for coating disbondment at elevated
temperatures because of high dry-film thickness (DFT) was evaluated through a
testing program and on-site inspections.
© 2011. Society of Petroleum Engineers
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- Original manuscript received:
10 February 2010
- Meeting paper published:
3 May 2010
- Revised manuscript received:
10 May 2010
- Manuscript approved:
25 June 2010
- Published online:
28 February 2011
- Version of record:
3 March 2011