Corrosion has been observed on a number of alloy 718 (UNS N07718) and alloy 825 (UNS N08825) gaskets from subsea connections. The gaskets were in contact with either weld overlaid alloy 625 (UNS N06625) or super duplex stainless steel hubs (UNS S32750). A few hubs also showed some limited corrosion in regions where severe gasket corrosion had occurred. Corrosion was more prevalent on jumpers that
had been exposed to sea water for a few months at alloy 718 (UNS N07718) gaskets in contact with alloy 625 (UNS N06625) weld overlay.
General observations were that short term exposures of up to 20 days did not result in corrosion but longer exposures of 40-50 days resulted in severe attack. A programme of work was carried out to determine the reason for the observed attack and to suggest ways of avoiding it in the future. This paper describes the findings of the study.
Kevwords: crevice corrosion, galvanic corrosion, sea water, gaskets, nickel base alloys, stainless steels