What is Sour Gas Corrosion Testing?

A simple, unnotched test specimen is loaded in static uniaxial tension (via proof ring) and placed in the environmental test vessel for up 720 hours. The absence of specimen fracture/cracking is acceptable, while cracking or fracture constitutes a failure. By testing a material at different stress levels, an apparent threshold stress level can be determined below which cracking due to SSC would not be expected.

A “C” shaped partial ring of material (typically from a tubular type product) is loaded circumferentially and placed in the environmental test vessel for up to 720 hours. The absence of specimen fracture/cracking is acceptable, while cracking or fracture constitutes a failure. By testing a material at different stress levels, an apparent threshold stress level can be determined below which cracking due to SSC would not be expected.

Unlike the pass/fail Methods A and C, the DCB test (Method D) measures resistance to environmentally assisted crack growth as a critical stress intensity factor, KISSC. A wedge loads the specimen at a starter notch before environmental exposure. Valid tests require crack growth (typically after 14 days). Lower-strength materials may need fatigue pre-cracking to initiate cracking.

NACE TM0316 uses four-point bend testing to assess metals—including carbon steels, low alloy steels, CRAs, and welded or clad materials—for resistance to stress corrosion cracking (SCC) and sulfide stress cracking (SSC).

Specimens are loaded in a four-point bend jig to apply a controlled tensile stress and exposed to one of four standard NACE TM0177 solutions (A–D) or a custom environment. After exposure, samples are examined for cracking.