Effect of Buffer System on the Sulfide Stress Cracking Susceptibility of Low-Alloy Steel

CORROSION ◽  
10.5006/2626 ◽  
2018 ◽  
Vol 74 (7) ◽  
pp. 788-800
Author(s):  
Kenji Kobayashi ◽  
Tomohiko Omura ◽  
Hisashi Amaya
Keyword(s):  
Partial Pressure ◽  
Buffer System ◽  
Low Alloy Steel ◽  
High Co2 ◽  
Co2 Partial Pressure ◽  
Stress Cracking ◽  
Test Conditions ◽  
Sulfide Stress ◽  
Ratio Condition ◽  
Sulfide Stress Cracking

The effects of a buffer system in test solution and CO2 partial pressure on sulfide stress cracking (SSC) susceptibility of low-alloy steel were investigated under pH 4.0 at 0.03 MPa H2S partial pressure. A double cantilever beam test was used to quantitatively evaluate SSC susceptibility. The corrosion rates and absorbed diffusible hydrogen concentration were also evaluated. Acetic acid/sodium acetate (acetate buffered solution) and carbonic acid/bicarbonate (bicarbonate buffered solution) buffered solutions were used as buffer systems in this study. From the results, in atmospheric pressure tests, KISSC values in bicarbonate buffered solutions were equivalent to or lower than those in acetate buffered solutions. In high CO2 partial pressure conditions, KISSC values in bicarbonate buffered solutions were much higher than those in acetate buffered solutions. At a high CO2 partial pressure and H2S partial pressure (pCO2/pH2S) ratio condition, hydrogen entry is considered to be greatly prevented by corrosion products probably containing amorphous iron carbonate. Presence of the corrosion product with high protectiveness produced in the high pCO2/pH2S ratio condition suggests the possibility that conventional test conditions using acetate buffered solutions are conservative or are equivalent test conditions for actual field conditions.

Effects of Environmental Factors on Hydrogen Absorption and Sulfide Stress Cracking Susceptibility of Low Alloy Steel

CORROSION ◽  
10.5006/3414 ◽  
2020 ◽  
Vol 76 (7) ◽  
pp. 698-706
Author(s):  
Kenji Kobayashi ◽  
Tomohiko Omura ◽  
Shinji Fujimoto
Keyword(s):  
Environmental Factors ◽  
Partial Pressure ◽  
Hydrogen Concentration ◽  
Critical Stress Intensity Factor ◽  
Low Alloy Steels ◽  
Diffusible Hydrogen ◽  
Solution Ph ◽  
Stress Cracking ◽  
Sulfide Stress ◽  
Sulfide Stress Cracking

In this study, the sulfide stress cracking (SSC) susceptibility of high-strength low alloy steels was investigated quantitatively. Double cantilever beam tests were used to evaluate the effects of environmental factors, namely pH, H2S partial pressure, and temperature, on the SSC. The corrosion rates and the absorbed diffusible hydrogen concentration were also determined. The critical stress intensity factor (KISSC), which signifies the SSC susceptibility, was mainly affected by the H2S partial pressure and the temperature. Even though the solution pH apparently affected the corrosion rate, the influence of pH on KISSC was small. Considering these results, the environmental contribution in each elementary process of the SSC phenomenon was discussed. The estimated local hydrogen concentration at the crack tip area, which clearly depends on H2S partial pressure and temperature, showed good correlation to the KISSC obtained in various sour conditions.

Formation of Microgrooving on C110 casing steel after Sulfide Stress Cracking Test

CORROSION ◽  
10.5006/3714 ◽  
2021 ◽  
Author(s):  
Christophe Mendibide ◽  
Claude Duret Thual
Keyword(s):  
Uniaxial Tensile ◽  
Cross Sectional ◽  
Testing Conditions ◽  
Stress Cracking ◽  
Test Conditions ◽  
Test Parameters ◽  
Sulfide Stress ◽  
Sulfide Stress Cracking ◽  
Sour Service ◽  
C110 Steel

NACE TM0177 is a commonly employed materials qualification standard specifying how Sulfide Stress Cracking (SSC) tests must be conducted and interpreted to verify the suitability of material application in sour service. This standard specifies through the so-called method A test (a tensile uniaxial environmental cracking test) that a material could be considered acceptable for sour service as long as no failure is evidenced after 720 hours of exposure, and no initiation of environmental cracking is observed on the reduced length of the specimen after macrographic observations. After cross-sectional observations, so-called “micro-grooves” can sometimes be evidenced on the surfaces of non-failed specimens. Such features can hardly be interpreted as SSC crack initiation sites considering their shape and depth. Experience, however, shows that the formation of these microgrooves appears to be dependent on test conditions and type of load. This paper presents the results of investigations on the parameters influencing the micro-groove formation on C110 steel after the method A uniaxial tensile SSC test. Test parameters influencing the groove formation are studied, and the results suggest that grooving is not considered as SSC initiation for the testing conditions used in this work

scholarly journals Sulfide Stress Cracking of C-110 Steel in a Sour Environment

2021 ◽  
Vol 2 (3) ◽  
pp. 376-396
Author(s):  
Sagar Tale ◽  
Ramadan Ahmed ◽  
Rida Elgaddafi ◽  
Catalin Teodoriu
Keyword(s):  
Partial Pressure ◽  
Hydrogen Permeation ◽  
Pressure Ratio ◽  
Optical Microscope ◽  
Mixed Gas ◽  
Stress Cracking ◽  
Sulfide Stress ◽  
Sulfide Stress Cracking ◽  
Partial Pressure Ratio ◽  
Grade Steel

The scope of this study includes modeling and experimental investigation of sulfide stress cracking (SSC) of high-strength carbon steel. A model has been developed to predict hydrogen permeation in steel for a given pressure and temperature condition. The model is validated with existing and new laboratory measurements. The experiments were performed using C-110 grade steel specimens. The specimens were aged in 2% (wt.) brine saturated with mixed gas containing CH4, CO2, and H2S. The concentration H2S was maintained constant (280 ppm) while varying the partial pressure ratio of CO2 (i.e., the ratio of partial pressure of CO2 to the total pressure) from 0 to 15%. The changes occurring in the mechanical properties of the specimens were evaluated after exposure to assess material embrittlement and SSC corrosion. Besides this, the cracks developed on the surface of the specimens were examined using an optical microscope. Results show that the hydrogen permeation, and subsequently SSC resistance, of C-110 grade steel were strongly influenced by the Partial Pressure Ratio (PPR) of CO2 when the PPR was between 0 and 5%. The PPR of CO2 had a limited impact on the SSC process when it was between 10 and 15 percent.

Sign in / Sign up

Export Citation Format

Share Document