Current testing standards provide details on how to determine Critical Stress Intensity Factor (KISSC) of C110 material (microalloyed AISI 4130 steel – UNS G41300) in 100% and 7% H2S. At 100% H2S, American Petroleum Institute (API)1 and National Association of Corrosion Engineers International (NACE)2 require a non-buffered Solution A for testing. For testing in 7% H2S, the test solution is buffered at pH 4.0 and N2 is the carrier gas. The European Federation of Corrosion Publication 16 (EFC)3 recommends a different test environment, in which the test solution is buffered to pH 4.5 for all H2S concentrations and the carrier gas is CO2 for testing in milder H2S environments. The recommended crack starter choices also vary. These test variables affect the final KISSC values.

This paper presents Critical Stress Intensity Factor (KISSC) data generated for two heats of standard mill produced C110 casing steel under varying applied loads and in three H2S environments - (i) NACE Solution A with no pH control using N2 as the carrier gas, (ii) NACE Solution A with no pH control with CO2 as the carrier gas, and (iii) buffered EFC solution with pH controlled at 4.5 using CO2 as the carrier gas. Double cantilever beam (DCB) samples from both materials were tested in NACE A and EFC solutions to the requirements of NACE Standard TM0177 Method D in various sour environments under a range of applied loads. The KISSC and KILIMIT data generated under three environments are compared. A relationship between KISSC - KILIMIT and KILIMIT - H2S is trended.

Subject
Test methods, Water, Materials, Hydrogen concentration, Stress intensity, Compliance, Sour environments, Acidity, Sodium chloride solution, Heat, Steel, Sulfide stress cracking, Samples
Keywords:
corrosion test, C110 casing, double cantilever beam (DCB), NACE MR0175, NACE TM0177, EFC 16, sour environment, sulfide stress cracking (SSC), stress intensity factor (KISSC)
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2014
Association for Materials Protection and Performance (AMPP)
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