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CORROSION 96
ABSTRACT A new electrochemical method for identification of the mechanism of corrosion fatigue crack growth (FCG) has been proposed. The method is based on the discovered regularity of an ambiguous effect of short-term cathodic polarization on the corrosion FCG rates. The regularity is a common one for high strength steels, titanium alloys and magnesium alloy tested, and it implies that short-term cathodic polarization accelerates the corrosion FCG by several times, when maximum stress intensity Kmax and corresponding FCG rate exceed certain critical values, but when Kmax and corresponding FCG rate are lower than the critical values, the same cathodic polarization (with all other conditions being equal) retards or does not almost influence the corrosion FCG. It is concluded that the accelerated crack growth at cathodic potentials is due to hydrogen-induced cracking (HIC) appearance. Therefore, the critical values of Kmax and corresponding FCG rate are regarded as the ones corresponding to the beginning of corrosion FCG according to HIC mechanism. INTRODUCTION For more than twenty years, the subject of corrosion fatigue crack growth (FCG) in high strength steels, titanium alloys, and magnesium alloys exposed to various aqueous solutions modeling natural and technological environments has been attracting considerable attention. In this period literature has accumulated a wide scope of experimental data. However, up to now there are no effective means of the protection of these materials against this fracture type. The search for protection means is complicated by the fact that quite a number of questions, which determine the possibility, mode and rate of corrosion FCG, remains unsolved as yet. Among the unsolved questions we should point out first of all is the question about the corrosion FCG mechanism. The mechanisms, which have been proposed to account for corrosion FCG, are not essentiallv8 different from those invoked in explaining stress corrosion cracking (SCC). The role of the two processes, i.e. hydrogen induced cracking (hydrogen embrittlement in the highly strained region just ahead of the crack tip) and local anodic dissolution (LAD) of metal at the crack tip, as possible mechanisms of corrosion FCG is discussed mainly. Here most of researchers, substantiating a dominant role of one of the mechanisms, either do not consider or reject the possibility of the crack growth by another mechanism. One of the reasons for the absence of a single opinion of the corrosion FCG mechanism seems to be the absence of conventional methodological approach to its identification, while this approach would be applied to any materials independently of their composition and microstructure. In the present paper, an attempt to identify the mechanism of corrosion FCG and to quantify the role of hydrogen induced cracking (HIC) and LAD during corrosion fatigue crack propagation in high strength steels, titanium alloys, and magnesium alloys has been made. For this purpose, the effect of electrochemical polarization on the corrosion FCG rates, as well as fracture surfaces have been studied using views developed elsewhere to examine SCC mechanisms.
- Materials > Metals & Mining (1.00)
- Energy > Oil & Gas > Upstream (1.00)
ABSTRACT This paper describes a model for the simulation of environmental changes within a stress corrosion crack under anaerobic conditions in a near neutral pH. carbon dioxide rich solution, Model simulations predict that a mildly acidic solution is produced after only.1 hours of exposure to the test solution. This pH decrease is primarily due to the formation of FeCO3 which alters the carbonate bicarbonate equilibrium. causing a lowering of pH. Once the concentrations of the carbonate species have been reduced in the crack, the exterior surface system can be considered to be in a differential carbonation system with the initial crack. INTRODUCTION Stress Corrosion Cracking (SCC)of pipeline steel is a phenomenon which has attracted considerable attention in recent months in Canada, The process has been associated with carbon dioxide rich. near neutral pH environments. The mechanism of this type of cracking has been shown to be different to that associated with the more familiar high pH SCC. Which has been known on gas transmission pipelines for the past thirty years. Crack extension rates measured from field studies arc approximately 2 x 10-8 mm/s. Electrochemical corrosion rates for polished pipeline steel coupons measured in solutions associated with neutral pH SCC. Vary within pH. At a pH of 6 the rate is approximately 3X 10-8 mm/s. whereas at a pH of 7 the rate is in the region of 5 x 10-9mm/s. These findings have led to the conclusion that the mechanism of neutral pH SCC is a stressed focused dissolution process: The solutions found associated with neutral pH SCC are in the range of pH 6.5 to 7.5. suggesting that the environment at the crack lip ~would have to be at a lower pH to enable a corrosion rate high enough to sustain a dissolution process. This paper discusses the development of a model for the simulation of the crack solution chemistry associated with stress corrosion cracks in a bulk solution similar to that found 011pipelines. The objective of the model development as to determine what changes in solution chemistry occur within a stress corrosion crack with time and identification of the important parameters associated with a dissolution based SCC mechanism. It is hoped that, by using such modeling procedures, the requirements for additional experimental research will be identified. The results of the computer simulations arc discussed in terms of transient pH and ion concentrations.
- Research Report > New Finding (0.34)
- Research Report > Experimental Study (0.34)
Microbially Influenced Corrosion of Fe, Ni, Cu, Al and Ti Based Weldments in a Marine Environment
Buchanan, Raymond A. (University of Tennessee) | Kovacs, Annette (University of Tennessee) | Lundin, Carl D. (University of Tennessee) | Khan, K.K. (University of Tennessee) | Danko, Joseph C. (University of Tennessee) | Angell, Peter (CNWRA) | Dexter, Stephen C. (University of Delaware)
ABSTRACT Weldments representative of a range of marine structural materials were exposed to a natural marine environment which was known from previous studies to induce microbially influenced corrosion (MIC). The natural environment was at a University of Delaware site on the Delaware Bay, Lewes, Delaware. Companion laboratory control tests were conducted at the University of Tennessee in 0.2 pm filtered Delaware Bay water and in synthetic seawater. The natural and control tests were conducted with weldments in both creviced and non-creviced conditions. Open-circuit potentials (OCPS) and corrosion rates (polarization-resistance measurements and microscopic examinations) were evaluated for all tests. The weldments studied were: 304L, 3161. and AL-6XN stainless steels; HY-80 and HSLA-80 low-alloy steels; Alloy 400 Ni-Cu alloy; 90-10 Cu-Ni alloy; 5086 aluminum alloy; and unalloyed titanium. In the non-creviced condition, ennoblement of the OCP, to varying degrees, relative to the laboratory control tests, occurred for all weldments. Clearly, a microbial effect at the Delaware Bay site was responsible for this ennoblement (higher OCP values). For the creviced condition, in most cases, ennoblement did not occur. Rather, the OCPS in the natural microbial environment were less than those in the laboratory control environments -- a result that could be rationalized in terms of higher crevice-corrosion initiation rates in the natural microbial environment. On comparison of corrosion rates in the natural Delaware Bay water with those in the laboratory control tests, it was determined that the microbial influence was one of significant corrosion acceleration for the 3041., 316L, Alloy 400, and 90-10 Cu-Ni weldments, with Alloy 400 experiencing the greatest degree of acceleration. Corrosion acceleration also occurred for the low-alloy steel weldments, HY-80 and HSLA-80, but to a smaller degree. Conversely, the microbial influence resulted in corrosion inhibition for the 5086 aluminum alloy and titanium weldments. For the AL-6XN weldment, the microbial influence produced corrosion inhibition in the non-creviced condition, but corrosion acceleration in the creviced condition. INTRODUCTION The goal of this study wm to evaluate the extent of marine microbially influenced corrosion (MIC) on a range of weldments representative of those employed in structural applications. Although numerous MIC investigations have been conducted on non-welded specimens in marine environments, more information is needed on the behaviors of welded materials, since welding probably is the most common method of structural fabrication. Furthermore, since the weldmodified material may differ from the base material in terms of chemical composition, chemical-composition uniformity, microstructure, or surface condition, it is reasonable to expect that the weld-modified material may respond differently than the base material with regard to the microbial effects associated with a natural marine environment. To accomplish the goal of this study, weldments representing a range of materials were exposed both to a natural marine microbial environment and to laboratory quasi-sterile control environments. Resultant corrosion rates and corrosion behaviors were evaluated and compared. To provide information relative to the causes of MIC in the natural environment, microbiological analyses were performed on water samples and on biofilms formed on the weldment surfaces.
- North America > United States > New Jersey (0.90)
- North America > United States > Delaware (0.90)
- North America > United States > Tennessee > Knox County > Knoxville (0.28)
ABSTRACT Stress corrosion cracking of line pipe from the soil side involves slow crack growth at stresses which may be as low as half the yield strength of the steel. The majority of failures experienced in various parts of the world are characterized by being associated with intergranular stress corrosion crocks, resulting from the presence of carbonatebicarbonate solutions with pH?s of about 9.5. More recently transgranular cracks, due to the presence of carbon dioxiclecontaining solutions having pH?s in the vicinity of 6.5, have been observed. The emphasis in this paper is on approaches to prevention and control, making use of the controlling parameters identified by research into the problem. For existing lines, control of the problem may be through manipulation of the stressing conditions and, in principle, control of the cathodic protection, with temperature control offering an alternative approach for cracking by the higher pH environment but not that of low pH. For new lines, the additional factors of steel composition, surface condition and coating system and quality maybe added to the above for control of the problem. INTRODUCTION Stress corrosion cracking: (SCC), from the soil side, of high pressure pipelines has occurred in several countries throughout the world over the last three decades or so. The great majority of those failures have involved intergranular cracking, hut more recent] y instances of transgranular cracking have been observed. The visible manifestations of these failures are groups, or colonies, of cracks oriented essentially longitudinally along the pipe and which can penetrate to various depths up to the wall thickness. Failure occurs when cracks penetrate the wall and result in a leak, or, when the wall is not penetrated, the crack or group of cracks reach a critical size, resulting in ruptures that can propagate for considerable distances beyond the ends of the initiating stress corrosion cracks if the fracture toughness of the steel is low. Intergranular SCC has been observed in pipes ranging over the diameters and wall thicknesses commonly encountered in high pressure gas transmission lines, fabricated by a variety of welding techniques and in seamless pipe. Almost all cases of SCC have been encountered in pipe installed for more than 10 years, with no failure of pipe that has been in service for less than 5 years. The compositions and properties of pipeline steels in which SCC has occurred cover the usual range of such steels, i.e. there is no evidence within that range that there are regimes of immunity, although laboratory tests show differences in the cracking propensities of different pipe steels. There are no equivalent data relating to transgranular SCC, which has, so far, mostly involved X65 grade material. However, since there have been relatively few failures of this form, and no laboratory tests to assess the susceptibilities of different steels, it would be unwise to assume that it is a problem only with X65 grade steel. Apart from crack morphology, there are other differences between the circumstances surrounding the intergranular and transgranular forms. Thus, with intergranular SCC, over 90% of failures have been within 16 km downstream from a compressor station, where both the temperatures and stresses are higher than further downstream. Gas temperatures at the times of service failures have been reported as ranging from 10 to 60°C, with most of the temperatures above 35 °C, and while gas temperatures can vary considerably with time, there are indications that where most service failures occurred temperatures were relatively high at times prior to failure. Moreover, results from laboratory tests in environments similar to those
ABSTRACT HSLA80, Corrosion fatigue, Crack growth rate, artificial seawater # ABSTRACT Fatigue crack growth rate experiments per ASTM E647 were performed on compact tension specimens of high strength low alloy structural steel (HSLA80, ASTM A71 O, base plate and HAZ region) in 3.5% NaCl, and artificial seawater solutions. The objective of the research was to investigate corrosion effects on crack growth rates, and threshold stress intensity factor range. Stress ratios for the tests were 0.1, and 0.8 while a cyclic loading was applied at a test frequency of 1. Comparison of the da/dN-AK curves in different environments shows that the fatigue crack growth rate of this steel increased in the presence of a corrosive species at its crack tip. The threshold stress intensity factor range was affected by the exposed environments, and it showed a drop from 12 MPa.mA0.5(for air) to 7 MPa. mA0.5(for artificial seawater and 3.5% NaCl solutions). Unfortunately, cathodic protection resulted in a higher crack growth rate for this steel(one order of magnitude), and some other protection system should be utilized. INTRODUCTION A common cause of the premature failure of structural components is corrosion fatigue cracking. The effects of corrosion fatigue are an important consideration in equipment and structures of ships, offshore platforms, mining, oil drilling rigs, aircraft, navigation communication towers, bridges, and underwater pipelines(1). High strengths low alloy structural steel has been historically used in ship building. Fatigue problems are more likely to occur in ships fabricated from high strength steel than low carbon steel unless there are some changes in ship design. The advanced unidirectional double-hull ship is an example of such a fatigue resistant design. The number of fatigue critical detail is reduced by eliminating transverse frames between bulkheads. The double hull design may help contain damage from leaking due to fatigue cracks. A cracking element of the double-hull framing system transfers load to adjacent members more easily than stiffened-panel construction, reducing the probability of catastrophic failure. In the event of fatigue cracking, the cracks must propagate around right-angle intersections. The multi-ended crack can be modeled as an idealized surface crack in a solid bar of the same outer dimensions as the box-section beam used in the double-hull. These ships are also likely to be fabricated from modern high strength low alloy (HSLA) steels that offer increased weldability, strength and toughness [2]. Several studies [2-7] have been conducted to investigate the fatigue behavior and fracture failure modes for ships built according to the advanced double hull design, the material used in this investigation was a copper precipitation-hardened steel conforming to Mil-STD-S-24645 (SH) Class 3, commonly referred to as HSLA80 (same as ASTM A71 O, grade A, Class 3). The objective of this investigation was to study the corrosion behavior of HSLA- 80 in marine environment. This investigation included general corrosion studies, electrochemical studies and fatigue crack propagation in different environments.
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
ABSTRACT The current technology for geothermal well drill ing is characterized by the use, often unsatisfactorily y, of drill pipes made of carbon steels, according to the standard practice in oil and gas fields. An experimental work has been carried out on laboratory heats and on industrial drill pipe in order to define criteria for the selection of innovative steels for geothermal applications. The Electro-Slag Remelting (ESR) technique applied to drill pipe materials was found to be effective in decreasing impurity levels (mainly sulfides), with positive effects on the mechanical characteristics (especially toughness) as well as on the resistance to environmental y assisted fracture. Nevertheless, the positive effect of steel cleanliness and of the improved mechanical properties on stress corrosion and fatigue corrosion sensitivity was found unable to completely solve the practical problems of failure in service. As a matter of fact, all the steel examined proved to be subject to stress corrosion cracking in the simulating geothermal environment. Environmental control by lime addition to the drilling mud, together with the use of ESR treated steels, proved to be very effective in overcoming the strong sensitivity to environmental assisted cracking in sour environments. INTRODUCTION Geothermal fluids have long been used in Italy for electric uses. The equipment used for drilling is generally derived from that used in the oil and gas industry and the drill pipes are made of quenched and tempered low alloy steels as stated by API specifications. Recent policy has been to increase drilling depth so as to reach new productive layers with higher temperatures (1,2). The aggressiveness of the endogenous fluids that are encountered at such depths is primarily due to the presence of high concentrations of carbon dioxide (C02), hydrogen sulfide (H2S), chlorides and other chemical species in lower concentrations. The very high temperature of geothermal fluids, often largely exceeding z500c, is very effective in increasing the corrosion rate and determining failures related to stress corrosion and fatigue corrosion. It thus appears that priority should be given to the assessment of new materials for geothermal applications to be used in drill pipes (3). Hydrogen embrittlement and sulfide stress cracking of high strength low alloy steels is a phenomenon well known and extensively studied in the oil and gas industry (4,8). Nevertheless, in the experience of geothermal energy exploitation, the drilling operating conditions are more critical due to the following reasons: the geological layers through which geothermal wel Is are drilled have peculiar characteristics so as the widely used drilling technology does not include the use of drilling mud; environmental control is more difficult and the drill pipe is in contact with the endogenous fluids; temperatures are decidedly higher than those typically involved in oil and gas drilling. As a consequence, complex environmentally assisted cracking phenomena such as anodic stress corrosion cracking, sulfide stress cracking and hydrogen embrittlement, have to be expected. High strength drill pipes can be subject to failure when in contact with acidic geothermal brines containing hydrogen sulfide, CO2, Cl- and other chemicals. Moreover, with such harsh drilling conditions, failure due to pure mechanical fatigue must be taken into account. The need to define criteria for the qualification of new materials for geothermal applications and to find practical and quick solutions to the corrosion problems found in service drove the experimentation towards already known and industrially available materials that can guarantee better reliability of t
- Europe > Italy (0.34)
- Europe > Netherlands (0.28)
- Well Drilling > Drillstring Design > Drill pipe selection (1.00)
- Reservoir Description and Dynamics > Non-Traditional Resources > Geothermal resources (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
ABSTRACT The risk of rapid pitting corrosion due to bacterial contamination has been studied by monitoring the natural coupling current flowing between two concentric electrodes. For sulfate reducing bacteria in general (SRB) and thiosulfate reducing bacteria in particular (TRB), the presence of thiosulfate and its utilization by the bacterial metabolism are shown to represent a major risk factor, leading to penetration rates greater than a centimeter per year. INTRODUCTION An abundant literature is already available on the corrosion of steels due to sulfate reducing bacteria (SRB). However, most of this work has been largely academic in nature, involving detailed analysis of laboratory tests, with no attempt whatsoever to simulate service conditions or to compare the results with field experience. For industrial operators, corrosion phenomena are a cause of large financial expenditure, whereas there is an unfortunate tendency for many laboratories to see them rather as a source of income. Microbially induced corrosion (MIC) must therefore be judged on the grounds of industrial criteria, and not on the basis of simple laboratory tests, however scientific and sophisticated they may be. In particular, it is important to emphasize that a corrosion rate has dimensions LT-l. In order to be meaningful in engineering terms, it must imperatively be expressed in units of wall thickness L and lifespan T. The technological unit employed is the mpy (roil per year) or the mm/y in the metric system. Laboratory measurements of corrosion rates rarely involve either roils or mm, It is therefore essential to convert the raw measurement units to mm/y. Unfortunately, there is an increasing tendency to publish unconverted measurements, for example with weight losses expressed in mdd (mg/dm2/day), or polarization resistances in Ohm.cm2. Because of this, many microbiologists who publish their work are unaware that they have studied non-phenomena. In industrial terms, the absence of corrosion signifies a rate of less than 0.1 mm/y. Thus, in equivalent units, anything less than 20 mdd or greater than 2000 0hm.cm2 does not merit being considered as microbial corrosion. Similarly, MIC is often implicitly limited to uniform attack, and studied accordingly. In the case of SRB, uniform corrosion often simply amounts to residual dissolution, sometimes without the author realizing it. Moreover, some workers have gone so far as to consider the SRB to be protective. Presumably, these people have never seen a real life case of breakthrough. In contrast to such unrealistic approaches, the general aim of the present study was firstly to explain a breakthrough in an oil sealine which occurred in less than a year in the Congo in 1990, and secondly to analyze the specific risk factors relating bacterial contamination to the occurrence of such rapid failure. The morphology of this service corrosion was clearly of the pitting type, involving regions a few centimeters in diameter, with penetration rates greater than a centimeter per year. A mechanism of pitting corrosion was suggested, in which the pH is locally regulated by the bacterial metabolizes, leading to differential acidification between the iron-depleted cathodic region surrounding the pit and the iron-enriched solution in contact with the central anode, in which iron sulfide is precipitated. This regulation of pH by bacteria has been observed experimentally in the laboratory. The occurrence of local galvanic coupling between a pit and its surroundings has also been demonstrated. The experimental technique has been optimized in order to facilitate the study of the risk factors which promote such coupling 8. The method consists in artificially initiating a pit w
- Materials (1.00)
- Health & Medicine (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Water & Waste Management > Water Management > Constituents > Bacteria (0.54)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
INTRODUCTION ABSTRACT In fertilizer production, storage and handling, corrosion inhibitors play a very important role in ensuring the durability of the equipment and plant structures. The plants handle very corrosive raw materials and several corrosive intermediates and by-products under operating conditions. Fluid velocity and high temperatures and pressures compound the corrosion problems. In this paper an attempt is made to review the materials commonly utilized in the fertilizer plants and the role of inhibitors in mitigating various corrosion problems encounter~ based on the chemicals commonly handled and the products generated and distributed. Corrosion inhibitors for liquid ammonium nitrate-urea fertilizer are described in detail. As in many other industries, corrosion inhibitors (CIS) are also used in the fertilizer industry to protect equipment and structures from corrosion. The problem of protecting the equipment used in storing and dispersing the fertilizers also impacts the ultimate customer. The strategy adopted in ensuring durability and safety of installations and equipment involves a judicious compromise between the selection of fully corrosion resistant materials and the utilization of relatively less corrosion resistant materials with adequate protective measures. The latter generally involve cathodic protection, protective coatings and inhibitor systems. CIS may sometimes be ignored by the plant personnel due to the unfamiliarity with the chemicals, or processes involved. Only in cases where the inhibitor application is the only viable corrosion protection method, is the prescription followed earnestly. During fertilizer production, virtually all kinds of corrosion problems are encountered14, under the prevalent conditions of elevated temperatures and pressures, the presence of very corrosive chemicals and the by-products handled, high fluid velocities, and abrasion, erosion, etc. Though all the corrosion problems cannot be solved using inhibitors alone, many of the CIS used in other industries can be used in the fertilizer industry as welL5. To combat stress corrosion, erosion corrosion, cavitation, etc. industrial problems by applying inhibitors alone is difficult, and practical experience needs to be relied upon heavily. For normal corrosive situations, recommendations for the optimum choice of materials for handling different products, with or without additional corrosion protection measures, are available in the literature,&9 along with the specifications for optimum inhibitor systems. Since the raw materials utilized and the products generated and handled are known, the problem of selection of the inhibitor system may appear to be simple and straight-forward. However, in practice, the choice and application of the proper CI system is not that simple, for the working conditions are severe and varied. A brief summary of the raw chemicals and the fertilizer products handled and the materials of construction utilized 10>1?is presented first. A review of the CIS used at various stages of fertilizer production is presented further. Experiences reported on the effectiveness of different types of CI formulations in the fertilizer industry are discussed and an attempt is being made in this paper to identify the areas where the problems still persist and how further research and development might stimulate the development of new inhibitor systems for application in the field of fertilizer systems.
- Europe (1.00)
- Asia (0.69)
- North America > United States > Texas (0.28)
- Materials > Chemicals > Agricultural Chemicals (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.93)
- Government > Regional Government > North America Government > United States Government (0.93)
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
Microstructural and Chemical Characterization of MIC Products From Stainless Steel Probes in SeaWater Using SEM and AFM Techniques
Perez, R. (UNAM Laboratorio de Cuernavaca) | Zaragoza-Ayala, Alejandro E. (N. Acuna, Univ Autonoma de Campeche) | Martinez, Lorenzo (Univ Nac Autonoma de Mexico) | Flores, O. (Univ Nac Autonoma de Mexico)
ABSTRACT The use of electron microscopy techniques have various applications in the corrosion research. Scanning electron microscopy (SEM) and the chemical analysis of the corrosion products are commonly found in the corrosion related literature. Also, microstructural characterizations based on transmission electron microscopy (TEM) and electron diffraction patterns are widely used. More recent microscopy techniques such as the atomic force microscopy (AFM) have also been used for corrosion research. One of the main advantages of this technique is that allows to perform microscopy observations in situ during corrosion experiments. In this work some application of these techniques to the study of microbiologically induced corrosion (MIC) of stainless steel in natural seawater are presented. INTRODUCTION Seawater is one of the most corrosive environments. Several studies have shown that when a stainless steel surface is exposed to natural seawater at moderate temperatures the open circuit. This increase in the (OCP) is attributed to the formation potential (OCP) increases with time of a biofilm on the surface. The formation of this slime and the production of metabolizes by microorganisms give rise to the formation of differential aeration and concentration cells thereby increasing the corrosion rate. Between the main group of microorganisms which are involved in the microbiological induced corrosion (MIC), the sulfate-reducing bacteria (SRB) are of particular concern. These bacteria are able to produce hydrogen sulfide (H2S) which is a highly corrosive agent. Also, the produced sulfide may react with solubilized iron to form FeS. This in combination with bacterial cell mass is an excellent plugging agent. There are several factors, such as dissolved oxygen, salinity, the hydrodynamics of the system, temperature etc., which can affect the corrosion of metals and alloys immersed in seawater. Therefore, the study of the influence of these factors on the biological activity are important to understand the MIC in marine environments. Surface analysis using SEM and AFM techniques were performed on 316L stainless steel samples exposed to natural flowing seawater for various periods of time, these results are also presented in this work.
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
INTRODUCTION ABSTRACT This paper addresses the many conceptual similarities that exist among structural materials subject to environmentally assisted cracking in high temperature water. While cracking has been viewed as a highly mechanistically and phenomenologically unique process for every material, temperature, environment, loading, etc., there is an increasingly strong basis for treating environmental crack advance processes of ductile alloys in hot water from a common mechanistic and predictive perspective. This paper addresses the roles of various materials (ranging from low alloy and carbon steels, to stainless steels, to high nickel alloys), water chemistries (e.g., including various BWR and PWR conditions), temperature (from <200 to >360°C), irradiation, etc. on the crack advance process. Viewed from the perspective of the crack tip system, differences once perceived as large (e.g., in corrosion potential for BWRS vs. PWRS) are now recognized as relatively small (e.g., crack advance always occurs at ??low potential associated with deaerated water (because of oxygen depletion in the crack). Additionally, since these materials rely on good passivity, and since creep increases with temperature, the importance to crack advance of film rupture and metal dissolution / repassivation is common to all of these cracking systems. While unique aspects must be acknowledged and modeled for specific materials (e.g., MnS dissolution in low alloy steels, thermal sensitization, irradiation effects) and specific water chemistries (e.g., effects of high sulfide levels, occluded chemistries, nickel metal stability at high H2 fugacity), the recognition of the broad similarities and the existence of a common underlying framework leads to a more complete understanding of and predictive approaches for environmentally assisted cracking in high temperature water. Stress corrosion cracking and corrosion fatigue of structural components in light water reactors are life limiting factors in their operation. Thus, a life prediction methodology for environmental cracking is required for design, lifetime evaluation of components in which cracks are found, and analyses of plant life extension. An essential element in predicting and controlling environmental cracking in high temperature water systems is the proper conceptual understanding of crack advance. Any conceptual framework must be confirmed by critical experiments, then quantified using an appropriate fundamental framework to create, ideally, a deterministic model for life prediction, A fundamental framework is acknowledged as essential, because the number of variables that affect environmental cracking are so large and inter-dependent that factorial (or other designs for) experiments are hopelessly expansive. Once a solid conceptual understanding is established, its use to conceive and evaluate mitigation approaches is very powerful, and its extension to related cracking materials and environments straightforward. This paper focuses on the conceptual similarities of the crack advance process in light water reactor environments, and provides evidence and examples of the many common characteristics and therefore modeling / predictive approaches that can be used in high temperature water. Of equal importance are the resulting improved design and lifetime evaluation approaches for environmental cracking, which is addressed elsewhere in more detail [1-91, together with the shortcomings of the existing design and lifetime evaluation codes. Brief examples are given of the use of this life prediction approach is given for a variety of cracking systems, such as stainless steels and nickel alloys in hot water.
- Materials > Metals & Mining > Steel (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Energy > Power Industry > Utilities > Nuclear (0.69)