NACE - TM0198
Slow Strain Rate Test Method for Screening Corrosion-Resistant Alloys (CRAs) for Stress Corrosion Cracking in Sour Oilfield Service
| Organization: | NACE |
| Publication Date: | 12 February 2004 |
| Status: | inactive |
| Page Count: | 21 |
scope:
General
This standard establishes a SSR test method for screening CRA materials (i.e., stainless steels and nickel-based alloys) for resistance to SCC at elevated temperatures in sour oilfield production environments. The fact that this test method is a screening method implies that further evaluation or additional experience may be required before materials selection decisions can be made.
This standard specifies reagents, test specimen, test equipment, determination of baseline material properties, environmental and mechanical test conditions, test procedure, and analysis and reporting of test results.
The test procedure can be summarized as follows: A test specimen is exposed to a continuously increasing uniaxial tensile stress imposed via a slow and constant extension rate in the presence of an acidic aqueous environment containing H2S, CO2, and brine at an elevated temperature. The ductility parameters (plastic elongation and reduction in area) obtained from evaluation of the test specimen along with visual observation of its gauge section and fracture surface morphology are used as indicators of the material's resistance to SCC in the test environment. These results are then compared with the results from a similar test conducted in an inert environment to quantify the resistance or susceptibility to SCC in the test environment.
Procedures for SSR testing shall be consistent with those provided in ASTM(1) G 129.8 Tests involving high pressure and/or high temperature shall be performed with procedures consistent with those provided in ASTM G 111.9 The only deviations from these procedures shall be those specifically stated in this standard.
Safety Precautions
H2S is an extremely toxic gas that must be handled with extreme care. (See Appendix A for a discussion of safety considerations and toxicity of this gas.)
Precautions must be taken to protect personnel from the hazards of rapid release of hot gases and fluids and explosion when working with the high-pressure, high-temperature test conditions.
This standard is not intended to include procedures for cyclic SSR testing. However, such procedures are currently under development and are in use in some laboratories.
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