A Sulphide Stress Cracking (SSC) test program has been undertaken on candidate forged bar stock martensitic stainless steel alloy UNS S41500 (F6NM) supplied by two different manufacturers.
The program comprised of sustained load stress corrosion tests, generally in accordance with NACE TM0177-2005 Method A. The main exception was that a range of test conditions were used. This included test solutions with two different chloride contents and pH levels ranging from 4.0 to 5.5, plus hydrogen sulphide contents in the conditioning gas ranging from 0.5 to 100kPa.
The results of this test program are presented as Sulfide Stress Cracking domain diagrams for both manufacturers alloy.
Kermad, Abdelhak (Saudi Arabian Oil Company) | Tanaka, Yasuhiro (Mitsubishi Heavy Industries, Ltd.) | Sabti, Tareq (Saudi Arabian Oil Company) | Tsuchiyama, Yoshihiko (Mitsubishi Heavy Industries, Ltd.) | Younes, Mourad (Saudi Arabian Oil Company) | Oba, Naotsugu (Mitsubishi Heavy Industries, Ltd.)
Material selection for waterwall and superheater/reheater tubing for a heavy liquid fuel-fired supercritical boiler was performed based on hot corrosion testing. This was carried out at varying temperatures through simulated firing conditions using heavy liquid fuel on bare carbon steel UNS K02599, low-alloyed steel UNS K11562, carbon steel with UNS N06022 weld overlay, and carbon steel with 50Cr-50Ni thermal spray coating for waterwall tubing; and on austenitic stainless steels UNS S34709, UNS S30432, UNS S31042, Ni-based alloys UNS N06617, Alloy 740, Ni-Cr-Fe alloys UNS S35045 and UNS N08810 for superheater/reheater tubing. Mg-based fuel additive, an inhibitor of hot corrosion, was also used in testing the superheater/reheater tubing. The results showed that carbon steel with UNS N06022 overlay and austenitic stainless steel UNS S31042 yielded the best performance for waterwall tubing and superheater/reheater tubing, respectively. The application of a Mg-based fuel additive also showed great merit in suppressing corrosion in the superheater and reheater sections. This test program constitutes part of a feasibility study for the design and construction of supercritical boilers to enhance power generation in the Kingdom.
The presence of hydrogen sulfide in high-pressure gas systems causes several complications. Sour gas corrosion is a major concern in the oil and gas industry due to the presence of localized corrosion. Hydrates can occur in these systems at high pressures and low temperatures. Sour gas decreases the pressure and increases the temperature at which hydrate formation occurs. Operators have used both corrosion inhibitors and kinetic hydrate inhibitors to decrease the capital requirements of developing sour high-pressure gas systems. The development of sour gas corrosion inhibitors that are compatible with kinetic hydrate inhibitors is a major requirement for qualifying corrosion inhibitors for these applications.
This paper describes results of laboratory work on the development of new corrosion inhibitors by performing corrosion performance and compatibility testing with two different kinetic hydrate inhibitors. The new corrosion inhibitors must meet various additional requirements which make the development process even more complex. The partitioning of a corrosion inhibitor between the oil and water phases significantly impacts inhibitor selection and treatment strategy. Additionally, the type of kinetic hydrate inhibitor employed in the process poses restrictions to the corrosion inhibitor chemistry selection process. General corrosion performance was addressed using mass loss and electrochemical data. Localized corrosion evaluation was performed using vertical scanning interferometry (VSI). The main advantage of this approach is in providing quantitative data for product performance differentiation for minimizing the risk of localized corrosion.
Double Loop-Electrochemical Potentiokinetic Reactivation (DL-EPR) is a valuable technique to test Type 304 stainless steel (SS) materials and components for the presence of grain boundary chromium depletion and assess material sensitization. This has practical relevance for the evaluation of susceptibility to intergranular stress corrosion cracking (IGSCC) of welded structures. The present study reports on work to develop DL-EPR methodology applied to UNS S30400 SS pipe butt-welds of relatively small size and having fusion zones irregular in shape, both of which present experimental difficulties to electrochemical evaluations. The primary challenge was to determine how to practically get an accurate DL-EPR signal from the relatively small heat affected zone (HAZ) that may be susceptible to IGSCC. A simple method was used to isolate the area of study that led to a relatively small solution potential drops during DL-EPR measurements. Measurements on a control material showed that smaller IR drops correlated directly with a measurably smaller degree of sensitization as measured by DL-EPR. A prototypic butt-weld was used to join two different heats of materials, one of which had a low carbon with high delta-ferrite content and the other of which had a high carbon content and no delta-ferrite. The DL-EPR process could detect the delta-ferrite in the low carbon material and also isolate DL-EPR degree of sensitization measurements to the HAZ of the high carbon material. In the process of this DL-EPR analysis, comparisons were made with two different grain boundary etch techniques.
Malarvizhi, S. (Avinashilingam Institute for Home Science and Higher Education for Women) | Shyamala, R. (Avinashilingam Institute for Home Science and Higher Education for Women) | Papavinasam, Sankara (CorrMagnet Consulting Inc.)
Use of biodiesel provides promising opportunities for immediately addressing our energy security issues. Being plant based, biodiesels are more hygroscopic and more readily biodegraded than fossil fuels and the introduction and widespread use of biodiesels in the existing fuel infrastructure may lead to increased problems of microbiologically influenced corrosion (MIC). Effective control and prevention of MIC require an underlying knowledge of the microbes that survive in biodiesel and the ingredients that help in their growth. This paper discusses the corrosion of aluminum and copper in Jatropha curcas biodiesel and its blends with commercial diesel under the influence of bacteria isolated from the sediments of stored jatropha biodiesel by mass loss measurements. The results indicate that both the metals show highest corrosion rate in B100.
Conventional(1) 13%-Chrome Martensitic Stainless Steels (MSS) have been selectively used as Oil Country Tubular Goods (OCTG) in sour environments as unexpected failures occurred by cracking in some cases. Accordingly, restricted sour service environment has been recommended for use of 13%Cr MSS tubulars in oil & gas production by the standard i.e., ANSI/NACE MR0175/ISO 15156(2).
However, variables & their limits responsible for cracking of 13%Cr MSS tubulars, are probably not exhaustively defined yet; sometimes operating companies devise and follow their own qualification programs to select 13%Cr MSS for application in sour environments.
Likewise, a material qualification program was taken up for API 5CT L80 13Cr(3) steel for the application of downhole tubulars in several sour production environments. Along with other observations, unexpected failures of the material were observed in testing within the specified limits currently mentioned in the standard.
This technical paper details the test program and evaluation of the test results to define a further reliable domain for use of L80 13Cr MSS in sour service as downhole tubulars, including need to revisit limits indicated in the standard.
Since high strength UNS N07022 alloy was introduced in 2006, it has seen use as bar for both drilling and completions and as Oil Country Tubular Goods for oil patch applications. This paper summarizes the uses and applications for sour service oil patch and refinery applications. The alloy has been incorporated into the MR0175/ ISO 15156 document for Materials for Use in H2S-Containing Environments in Oil and Gas Production. The UNS N07022 alloy has been tested at MR0175 Level VII Environment with 5 g/L elemental sulfur and to Modified NACE(2) Level VII, 25% NaCl + 1,000 psi (7000 kPa) CO2 + 1,000 psi (7000 kPa) H2S at 550°F (2880C). The UNS N07022 alloy maintains mechanical properties over the -3000F to 5000F (1500C to 2600C ) temperature range with stability to 7000F (3700C) for >100,000 hours for refinery applications. Also, the UNS N07022 alloy is now included in the MR0103/ ISO 17945 Corrosion Prevention and Control for Oil and Gas Production, Petroleum Refining, and Gas Processing Industries. The UNS N07022 alloy has been qualified for subsea and marine fastener applications where no other alloy has the strength and corrosion resistance required. This paper reviews new metallurgy, mechanical properties and corrosion resistance, along with areas of application of the alloy.
This paper concentrates in defining an equation for crack length of a specimen Single Edge Notch Bend – Four Point (SENB-4P), applying the so-called Back-face Strain (BFS) method for a large extension and precision. The specimen type SENB-4P is well known and used in fatigue testing. The standard (ISO 12108)1,(1) provides a complete description of the specimen SENB-4P, however, this standard does not specify how SENB-4P could be used applying a BFS method to measure crack growth during a fatigue test. Moreover, there is lack of the literature concerning with BFS method applied to SENB-4P specimen for measuring crack propagation2. The existing work presents a relative short crack length with high level of imprecision. It is noteworthy that the majority of fatigue tests have a crack monitoring via Direct Current Potential Drop (DCPD), however its use in corrosive media is something still quite questionable and costly. In this work, two methods were used: simulation by Finite Elements Analysis and Fatigue Testing (air and in corrosive media), with monitoring of crack, a SENB specimen of API 5L X70 steel(2) , widely used in offshore pipelines. A methodology is presented herein, for using the technique of BFS in the specimen immersed in corrosive medium SENB. At the end of the test, the fatigue curves were compared to the curves of (BS 7910)3,(3).
Kobayashi, Kenji (Nippon Steel & Sumitomo Metal Corporation) | Hara, Takuya (Nippon Steel & Sumitomo Metal Corporation) | Mizuno, Daisuke (JFE Steel Corporation) | Ishikawa, Nobuyuki (JFE Steel Corporation) | Tada, Eiji (Tokyo Institute of Technology)
Hydrogen Induced Cracking (HIC) is a major issue for line pipe steels exposed to sour environments. In general, 5.0 wt% NaCl and 0.5 wt% CH2COOH solution with 0.1 MPa H2S provided by NACE TM0284 as solution A is used to evaluate the HIC resistance of steel products. However, in many cases, the test condition is too severe compared to the actual field conditions. Therefore, establishment of an appropriate HIC evaluation method under mildly sour conditions has been the subject of considerable investigations in recent years. In this study, the influences of balance gas (N2 and CO2) and specific solution volume on pH stability and sour corrosion behavior of carbon steel were investigated in order to recommend an appropriate test solution for mildly sour HIC evaluation in a specified pH condition. The remarkable pH shift during a long term HIC test was observed by using 0.05N acetate buffer solution, even though an appropriate balance gas and a large specific solution volume were selected. In contrast, 0.93N acetate buffer solution showed excellent pH stability during long term HIC tests even in low pH and low H2S partial pressure conditions regardless of balance gas selection and specific solution volume. The pH stability can contribute to stable hydrogen entry to the material and the correct HIC evaluation. Therefore, from the viewpoints of convenience and effectiveness for evaluating the resistance of steels to HIC in a specified pH condition, an acetate buffer solution including high total amount of acetic acid and sodium acetate is desirable.
Coupons simulating the coating defects have been used to evaluate cathodic protection level of steel structures. This paper aims to provide requirements for coupon AC current density as affecting AC corrosion of cathodically protected steel pipelines. The field investigation into the polyethylene coated 400 mm diameter natural gas transmission pipeline paralleling a 25 kV AC transit system which operated at frequency of 50 Hz was carried out. The steel coupon was connected to this pipeline with the cathodic protection applied. The four parameters, that is, coupon on-potential, coupon instant-off potential, coupon DC current density, and coupon AC current density were acquired by using the new coupon technology with high data sampling rate of 0.1 ms and 16-bit. It was thought that the requirements to regard the coupon AC current density for a single period of commercial current frequency as affecting AC corrosion could be: 1) polarity reversal; 2) consistency with commercial current frequency; 3) small distortion factor of a waveform.