Performance of Stressed CRAs in Contact With Elemental Sulfur in Highly Sour Brine

Normal size round tensile specimens of CRAs (Alloy 28, Alloy 31, Alloy 59, Alloy 625, Alloy 825 and Alloy 904L) with a weld in the middle of the test section were tested for 720 h under 90% of actual yield strength in contact with elemental sulfur (on the whole test section) and fully submersed in oxygen-free brine with 180,000 mg/L chloride (partly in the presence of oil-based inhibited sulfur solvent) at 50 and 100°C under higly sour conditions (cold pressure:17 bar H₂S, 10 bar CO₂). None of the test specimens suffered from any visual corrosion attack. Corrosion rates calculated from surface related mass losses were in all cases far below 0.1 mm/y. The highest integral corrosion rates were observed at Alloy 28 (0.08 mm/y) and Alloy 31 (0.04 mm/y) in pure brine at 100°C. In all other corrosion systems the integral corrosion rates were found below 0.02 mm/y.

The paper discusses also the basic methodologies of corrosion testing in the presence of elemental sulfur.