Corrosion behavior of alloy 31-UNS NO8031 - under conditions of oil & gas production

摘要

The corrosion behaviour of alloy 31 (UNS N08031-31Ni-27Cr-6.5Mo - 1.2Cu - 0.2N - bal. Fe) was tested in laboratory and field tests in seawater with and without additions of CO{sub}2 and/or H{sub}2S in slow strain rate tests, and in SSC (Sulphide Stress Corrosion) tests according to NACE MR0175. The results demonstrate a high resistance of alloy 31 to localised corrosion. Due to the high chromium and molybdenum concentration, its resistance to pitting and crevice corrosion in chloride-contaminated seawater is significantly higher than that of alloy 28 and alloy 825 and it equals that of typical nickel base alloys like alloy 625. Alloy 31 is not sensitive to chloride-induced stress corrosion cracking, either with or without H{sub}2S, or sulphide stress cracking. Alloy 31 is approved for sour gas applications up to LEVEL VI in NACE MR 0175. The combination of properties makes alloy 31 an attractive choice for components in oil and gas production including wire-lines, umbilicals, tubing, piping and topside application.