This study investigates several NACE TM0177 test solutions adjusted to the pH relevant to flexible pipe applications. Due to the low ratio of solution-to-steel surface area for the annulus, the environment readily supersaturates with Fe2+, and the pH is consequently in the range of 5.0-6.5. This makes the choice of test solution not straightforward.

Six types of carbon steel wires with known different mechanical properties and H2S resistance were exposed to pH-adjusted NACE TM0177 Solutions B, C, and D adjusted to the pH level of 5.1–5.4 under the purging condition of 1.0% and 1.5% H2S in CO2 at ambient pressure for 720 hrs. The sour resistance results from the different solutions were evaluated and compared with results obtained in an unbuffered solution (5.0 wt% NaCl solution). The results discussed in this paper showed that the test solutions with different buffer capacities have a limited impact on the sour test result in conditions relevant to flexible pipe annulus and that results obtained in any of the solutions should be considered equally valid.

Subject
Environmental cracking, Hydrogen induced cracking, Test methods, Piping, Corrosion rate, Annulus, Wiring, Corrosion reactions, Acetates, Acidity, Sodium chloride solution, Hydrophobic interaction chromatography, Sulfide stress cracking
Keywords:
Hydrogen-induced cracking, Electrolyte, Sulfide stress cracking (SSC), Oil/gas/petrochemical
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2023
Association for Materials Protection and Performance (AMPP)
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