Is sulfide stress cracking an anodic or a cathodic process. Generally, hydrogen embrittlement is classified under two broad categories based on the. Sulfide stress cracking is also called hydrogen sulfide cracking, sulfide cracking, sulfide. Risk ranking of cracking failures of duplex stainless. In fact, some authors have used the term hydrogen embrittlement to refer to ssc. Depleted reserves mean that energy companies are now being forced to develop more and sourer fields, containing hydrogen sulfide h 2 s. Another hydrogen embrittlement failure mode that can be a concern in the oil and gas industry is hydrogen induced stress cracking hisc, where hydrogen is introduced when the material is under cathodic protection in seawater. Ihac and heac are distinguished by the source of the offending h supplied to the crack tip fracture process zone fpz, but otherwise share common aspects. Sulfide stress cracking ssc occurs at locations where atomic hydrogen is able to diffuse at sites of high internal stress, such as grain boundaries, inclusions and regions of triaxial stress at notches. If the presence of hydrogen sulfide causes entry of hydrogen into the component, the cracking phenomenon is often termed sulphide stress cracking ssc. Environmentally assisted cracking eac is a general term that includes processes such as stress corrosion cracking scc, hydrogen embrittlement he, sulfide.
Sulfide stress cracking is also called hydrogen sulfide cracking, sulfide cracking, sulfide corrosion cracking and sulfide stress corrosion cracking. Investigators, after discarding embrittlement as a. Bend and tensile tests were conducted to establish the threshold condition for cracking in hubs on a subsea manifold subject to cathodic protection. Sulfide stress cracking ssc testing southwest research. Hydrogen embrittlement embrittlement is a phenomenon that causes loss of ductility in a material, thus making it brittle. If the presence of hydrogen sulfide causes entry of hydrogen into the component, the cracking phenomenon is often termed sulphide stress cracking ssc the use of cathodic protection for corrosion protection if the process is not properly controlled. The major hazards of h 2 s are its ability to cause rapid damage to health or sudden death due to accidental exposure and metal integrity failure due to general corrosion or cracking. Admittedly, direct evidence to this effect is limited. Dec 19, 2019 sulfide stress cracking ssc is a type of hydrogen cracking which presents a cathodic embrittlement mechanism. A marked difference in material response under loadcontrol and displacementcontrol was observed. Section page tables iii figures iv definitions v acronyms vi foreword vii 1. The mechanism of sulfide stress cracking involves a combination of stress corrosion cracking and hydrogen embrittlement. Effect of microstructure and crystallography on sulfide. Hydrogen stress cracking is a form of hydrogen embrittlement that occurs when corrosion from acids like wet hydrogen sulfide and hydrofluoric acid cause atomic hydrogen to penetrate hardened or higher strength steels and cause stress cracking.
Abstract this paper presents results from a testing program designed to investigate sulfide stress cracking susceptibility of local hard areas in weld heat affected zones evaluated by 4point bend testing. When placed in proximity to tensile stresses, embrittlement and the beginnings of brittle fracture may occur. Sulfide stress cracking ssc is a form of hydrogen embrittlement which is a cathodic cracking mechanism. Sulfide stress corrosion cracking, also known as sulfide stress cracking ssc, is a stress corrosion cracking phenomena that occurs in the presence of hydrogen sulfide. Oil industry experience with hydrogen embrittlement and stress corrosion cracking. Hydrogen embrittlement he also known as hydrogen assisted cracking hac and hydrogen induced cracking hic, describes the embrittling of metal after being exposed to hydrogen. Hydrogen sulfide h 2 s is a naturally occurring gas that can be deadly to humans and corrosive to oil and gas equipment, especially in the presence of water. Susceptible alloys, especially steels, react with hydrogen sulfide, forming metal sulfides and atomic hydrogen as corrosion byproducts. This is a type of deterioration which can be linked to corrosion and corrosioncontrol processes. Note ssc is a form of hydrogen stress cracking hsc and involves embrittlement of the metal by atomic hydrogen that is produced by acid corrosion on the metal surface. Sulfide stress cracking of nickelcontaining lowalloy.
All materials susceptible to hydrogen embrittlement are also very susceptible to stress corrosion cracking. Hydrogeninduced cracking hic and sulfidestress cracking ssc are two hydrogen embrittlement phenomena that can fracture steel 5, 6. The role of hydrogen in sulfide stress cracking of low alloy. When tensile stresses are applied to a hydrogen embrittled component it may fail prematurely. Hydrogen uptake is promoted in the presence of sulfides. The role of hydrogen in sulfide stress cracking of low. The influence of chemical composition and microstructure of api linepipe steels on hydrogen induced cracking and sulfide stress corrosion cracking. In the 19th century, petrus johannes kipp, a dutch pharmacist invented a device that would generate a variety of gases using liquids and solids as regents. Definition of sulfide stress cracking ssc iadc lexicon. Cracking of metal involving corrosion and tensile stress residual andor applied in the presence of water and h 2 s.
Ssc is a form of spontaneous brittle breakdown in occurring in highstrength. The variation of the name is due to the lack of agreement in the mechanism of failure. Pdf sulfide stress corrosion cracking and hydrogen. The most common types of mechanically assisted corrosion are stress corrosion cracking scc, erosion and abrasioncorrosion tribocorrosion, cavitation corrosion, and corrosion fatigue. There are maximum acceptable h 2 s concentration limits in sale quality oil and gas, which require. Sulfide stress cracning ssc is a form of hydrogen embrittlement which is. Hydrogen damage can lead to economic losses and human casualties 4. Sulfide stress cracking is a form of hydrogen embrittlement that occurs in high strength steels and in localized hard zones in weldment of susceptible materials. Sulphide stress cracking is a particular occurrence of hydrogen embrittlement at least for the alloys considered, and in the test conditions envisaged, where the hydrogen is generated as part of the cathodic corrosion reaction. Jul 25, 2017 sulfide stress cracking ssc is a form of hydrogen embrittlement which is a cathodic cracking mechanism.
Sulfide stress cracking ssc cracking of metal involving corrosion and tensile stress residual andor applied in the presence of water and h 2 s note ssc is a form of hydrogen stress cracking hsc and involves embrittlement of the metal by atomic hydrogen that is produced by acid corrosion on the metal surface. If applied current makes the specimen more anodic and accelerates cracking, it is a case of stresscorrosion cracking. The bp international centre for advanced materials 1,362 views. Hydrogen induced cracking of low strength steels in. Hydrogeninduced cracking can occur if the metal is subject to static or cyclic tensile stress. In this chapter the terms eac and scc are generally interchangeable. If applied current makes the specimen more anodic and accelerates cracking, it is a case of stress corrosion cracking. The risk of hydrogen embrittlement of steels is a primary concern for material development in oil and gas production. Sulfide stress cracking ssc is a type of hydrogen cracking which presents a cathodic embrittlement mechanism. Stresscorrosion cracking scc and hydrogen embrittlement are differentiated by their responses to the applied current and mode of cracking. Stress cracking is a form of hydrogen embrittlement.
The effect of nonmetallic inclusions in particular that of sulfides on the pitting corrosion mechanism has been the subject of numerous investigations. Hydrogen embrittlementsulfide stress cracking h2s grampi1 materials 26 sep 03 01. Sulfide stress cracking of steels it is generally accepted that ssc is a form of hydrogen embrittlement cracking in most high strength steels. Hydrogen sulfide cracking of carbon and alloy steels. Development of sweet co 2 containing oil and gas fields is fast becoming a thing of the past. Stress corrosion cracking and hydrogen cracking are two important forms of environmental cracking which can cause serious failures in the oil and gas, pipeline, process and many other industries. The effect of sulfide inclusions on the susceptibility of. Hydrogen sulphide stress corrosion cracking in materials for.
Sulfide stress cracking an overview sciencedirect topics. It should not be confused with the term stress corrosion cracking which is an anodic cracking mechanism. Hudgins c, mcglasson rl, mehdlzadeh p, rosborough wm. How to avoid h2s embrittlement in instrumentation connections. Hydrogen atoms can diffuse into metals, making them brittle. Hydrogen is present in minute quantities in steel, usually less than 1 part per million, but is attracted towards stress. It is a complex process that is not completely understood because of the variety and complexity of mechanisms that can lead to embrittlement.
Sulfide stress cracking of nickelcontaining lowalloy steels. Sulfide stress cracking is also called hydrogen sulfide cracking, sulfide cracking, sulfide corrosion cracking and sulfide stresscorrosion cracking. Hydrogen embrittlement is a function of the hydrogen absorption characteristics of the metal in the aggressive environment, which is the formation of molecular hydrogen from atomic hydrogen within the metal structure 160. It should not be confused with the term stress corrosion cracking which is. In r n tuttle and r d kane, editors, h 2 s corrosion in oil and gas production a compilation of classic papers, pages 162176. Effect of coldwork on sulphide stress cracking resistance.
At present there are two main theories for sulfide corrosion cracking, namely hydrogen embrittlement mechanism and stress corrosion cracking mechanism. Mechanisms that have been proposed to explain embrittlement include the formation of brittle hydrides, the creation of voids that can lead to bubbles and pressure buildup within a material and e. With a tensile stress or stressintensity factor exceeding a specific threshold, the atomic hydrogen interacts with the metal to induce subcritical. Some researchers consider sulfidestress cracking a type of stresscorrosion cracking, while others consider. Hydrogen induced cracking can occur if the metal is subject to static or cyclic tensile stress. An externally applied load is not required as the tensile stresses may be due to residual stresses in the material. Sulfide stress corrosion cracking and hydrogen induced cracking of a216wcc wellhead flow control valve body article pdf available in case studies in engineering failure analysis. Hydrogen sulfide is known to cause or assist in the mechanism of cracking with many alloy types including low carbon steels, low alloy steels, alloy steels, tool steels.
Hydrogen sulfide is a colorless, very poisonous, flammable gas with the characteristic foul odor of rotten eggs. Pdf sulfide stress corrosion cracking and hydrogen induced. It involves the ingress of hydrogen into a component, an event that can seriously reduce the ductility and loadbearing capacity, cause cracking and catastrophic brittle failures at stresses below the yield stress of susceptible materials. A pitting type corrosion and sulfide stress cracking ssc. The hydrogen is a result of the increased cathodic reaction, hydrogen ion reduction, on the stainless steel surface. Jun 05, 2017 stress corrosion cracking scc and hydrogen embrittlement are differentiated by their responses to the applied current and mode of cracking.
Recent experience has demonstrated the risk of sscc and hic, sometimes known as hydrogen embrittlement he, of low strength steels subject to high residual stress derived from fabrication techniques. Types of corrosion materials selection guide swagelok. Hydrogen embrittlement he a permanent loss of ductility in a metal or alloy caused b y hydrogen in combination with stress, either externally applied or internal residual stress 1. In the absence of residual stress or external loading, environmental hydrogen embrittlement is manifested in various forms, such as blistering, internal cracking, hydride formation, and reduced ductility. Highstrength steels with improved sulfide stress cracking resistance. Corrosionpedia what is sulfide stress cracking ssc.
Hydrogen sulfide has been studied for hundreds of years. The national association of corrosion engineers nace test method tm0177 is widely used to qualify metals for resistance to sulfide stress cracking and stress corrosion cracking in h 2 s environments. It is generally accepted that sulfide stress cracking ssc failures are the result of hydrogen embrittlement. This term should not be confused with stress corrosion cracking scs, since this is anodic in nature.
Hydrogen embrittlement cracking of superduplex steel twi. Jun 16, 2015 when hydrogen atoms diffuse into the metal, they can cause loss of ductility and loadbearing capacity. In his view, hydrogen stress cracking was only associated with higher strength steels. Wet hydrogen sulfide h2s cracking inspectioneering. The threshold stresses to cause cracking are commonly below the yield stress of the material. Hydrogen embrittlementsulfide stress cracking h2s metal. On the evaluation method of sulfide stress cracking susceptibility of carbon and low alloy steels.
Often, it is important to determine unambiguously by which of these mechanisms failure occurred, in order to suggest the right actions to prevent failure recurrence. Sulfide stress cracking susceptibility of local hard areas. Sulfide stress cracking is a form of hydrogen embrittlement that occurs in highstrength steels and in localized hard zones in weldment of susceptible. The purpose of this paper is to provide the experimental evidence which establishes the causality of hydrogen and the contributory roles of h 2 s and anodic dissolution. This is true for both the general and local corrosion mechanisms, like pitting corrosion, stress corrosion cracking scc, and hydrogen embrittlement he. Hydrogen assisted cracking of high strength alloys richard p. Sulfide stress cracking is a form of hydrogen embrittlement that occurs in highstrength steels and in localized hard zones in weldment of susceptible materials. Environmentally assisted cracking eac is a general term that includes processes such as stress corrosion cracking scc, hydrogen embrittlement he, sulfide stress cracking ssc, liquid metal embrittlement lme, and corrosion fatigue cf. When placed in proximity to tensile stresses, embrittlement and the. Hydrogen assisted cracking of high strength alloys richard. Materials and corrosion trends in offshore and subsea oil and gas production.
Hydrogen embrittlement also known as hydrogen assisted cracking and hydrogeninduced cracking, describes the embrittling of metal after being exposed to hydrogen. Sulfide stress cracking ssc occurs at locations where atomic hydrogen is able to diffuse. Effect of coldwork on sulphide stress cracking resistance twi. Pdf stress corrosion cracking and hydrogen cracking. This penetration can lead to the brittle fracture of materials that are normally ductile when hydrogen happens to be present in their environment. Mechanics of hydrogen diffusion and embrittlement duration. However, the evidence heretofore has been mostly circumstantial. The h2s causes the hydrogen to enter the metal structure rather than bubble off from the surface. To protect from ssc, hic hydrogen induced cracking and other damage mechanisms, refiners use a variety of defenses. With a tensile stress or stress intensity factor exceeding a specific threshold, the atomic hydrogen interacts with the metal to induce. The issue is especially acute in the middle east, where new oil and gas fields suffer from increasingly higher concentrations of h 2 s. Sulfide stress cracking is the cracking of a metal under the combined action of tensile stress and corrosion in the presence of water and hydrogen sulfide a form of hydrogen stress cracking. The effects of sulfide stress cracking on the mechanical properties.
Hydrogen embrittlement failures are frequently unexpected and sometimes catastrophic. Sulfide stress cracking of steels for api grade n80 tubular products. Some researchers consider sulfide stress cracking a type of stress corrosion cracking, while others consider. Although the different forms of hydrogen embrittlement do not require localized corrosion, hydrogen stress cracking hsc, sulfide stress cracking ssc. The material was sensitive to hydrogen embrittlement stress corrosion as a consequence of its microstructure. Hydrogen induced cracking hic and sulfide stress cracking ssc are two hydrogen embrittlement phenomena that can fracture steel 5, 6. Over time he can lead to cracking usually at submicroscopic levels or catastrophic failures of a brittle nature, at applied stress levels that are well below the yield strength or design strength of a given alloy.
Hydrogen sulphide corrosion cracking of steel corrosion. Materials and corrosion trends in offshore and subsea oil and gas production publication. Hydrogen embrittlement, journal articles, physical metallurgy, sulfide stress cracking tagged with. One of the more common problems is ssc, sulfide stress cracking.
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