ABSTRACTBiocides and corrosion inhibitors can decrease corrosion in stagnant and flowing systems, like storage tanks and pipelines. We have used 1 ml syringe columns packed with 60 carbon steel beads (55 mg each), which were continuously injected with the effluent of an SRB continuous culture chemostat, to monitor corrosion under flow conditions. A constant flow rate of 0.5 ml/hr was maintained throughout. General corrosion rates (CRs) were determined after 45 days of flow by measuring the weight loss of acid-treated beads. Medium entering the chemostat contained sulfate (10 mM) and formate (20 mM) for the growth of SRB. Effluent of the chemostat with 5 mM sulfate, 5 mM sulfide and high numbers of SRB was then continuously injected into the syringe columns. CRs of beads in these columns were 0.1 mm/yr. Periodic biocide treatment (2 h of 300 ppm every 5 days at the same flow rate) decreased CRs on average by 60% for two of five biocides tested, indicating control of corrosion in the system. In contrast, a single exposure of the carbon steel beads to a water-dissolved corrosion inhibitor at the start of the experiment decreased CR by 50%, whereas single exposure to two diesel- dissolved corrosion inhibitors decreased CR by 90-98%.INTRODUCTIONThe annual cost of internal corrosion in the oil and gas industry is significant and affects both stagnant (tanks) and flowing systems (pipelines)1,2. The involvement of microorganisms in this process is commonly referred to as microbially-influenced corrosion (MIC)3. Sulfate-reducing bacteria (SRB) are well known MIC agents, although other bacteria, e.g. acetogenic bacteria or other acid producing bacteria (APB) or methanogenic archaea can also be involved4,5. SRB act by producing sulfide, which reacts with steel in a chemical MIC (CMIC) mechanism, or by using iron directly as electron donor for sulfate reduction in an electrical MIC (EMIC) mechanism5. Like other forms of corrosion MIC can be prevented by the use of corrosion inhibitors or by the application of electrochemical methods, such as cathodic protection6,7. In addition, biocides are often used to kill SRB and other MIC-causing microorganisms8. A problem in killing corrosive bacteria is that these can be free-floating or part of the biofilm-scale attached to the tank or pipeline wall9. These are commonly referred to as the planktonic and sessile populations. The latter are often more difficult to kill because the surrounding biofilm- scale may not be easily penetrable by biocide10. Treatment of stagnant systems is inherently easier than that of flowing systems. The volumes of fluid in the latter are large and because biocide is expensive one has to choose between a continuous low dose of biocide or a high dose of limited duration, often referred to as a slug8. Injecting slugs of biocide into a flowing system is considered most efficient, because lower concentrations may not penetrate the biofilm-scale or may lead to a biocide-resistant biofilm11.
ABSTRACTTraditional water treatment methods pose several challenges to large-vessel preservation. The economics of continuous dosing and environmental restrictions concerning the disposal of treated water need to be considered. One solution to these challenges involves the application of an immiscible corrosion inhibiting oil partition on the water surface (henceforth referred to as a “float coat”). This paper will highlight challenges of traditional preservation methods and examine the efficacy of one commercial float coat (henceforth referred to as “Product A”).INTRODUCTIONLarge vessel preservation is typically accomplished through one of two methods: chemical treatment of water during hydrotesting or heavy-duty epoxy coating systems. These treatment systems have proven to be effective. However, novel approaches to large vessel preservation provide an opportunity to overcome challenges involved with more traditional preservation methods.Chemical TreatmentAboveground storage tanks (ASTs) in the petroleum industry come in a wide variety of sizes, ranging from modest sizes of 200 m3 up to storage volumes in excess of 100,000 m3, 1. For even the most modest dosage rates of chemical treatment at 500 ppm, costs can exceed to $2.5 million for more than 115 m3 of chemical treatment.CoatingsCoatings can be separated into removable, or “temporary” coatings, and permanent coatings. After the application of either type of coating, the proper amount of cure time must be allowed for the coating to achieve peak performance. Typical recommendations call for one week of cure time. During this time, no maintenance or testing can be performed on coated areas, resulting in lost time and productivity.For tanks with a 91.4 m diameter and 18.3 m wall height1, the total wall surface area is approximately 5300 m2. Given a spread rate of 3.7 m2 per liter, over 1500 liters of the coating are required, costing upwards of $40,000 USD. While removable or temporary coatings typically cost less than permanent coatings, the reapplication of any coating for long term preservation would require significant labor cost for surface preparation and application. Finally, lost time (for product application and cure time) is also a considerable factor resulting in lost profits.
ABSTRACTMagnesium (Mg) alloys are gaining interest for biodegradable medical implant devices due to a good combination of mechanical properties and biocompatibility. Nevertheless, the fast degradation rates of Mg and its biocompatible alloys in the aggressive physiological environment impose limitations on their clinical applications. This necessitates the development of Mg based implants with controlled degradation rates to match the kinetics of the bone and tissue healing process and to avoid any complications or issues that might negatively impact surrounding tissues. The current study presents alloy design and thermomechancial processing to optimize the mechanical and biological properties of a new proprietary Mg based alloy. Its corrosion profiles have been evaluated by a combination of in vitro and in vivo experimental studies. The corrosion rates of laboratory samples and prototype devices have been examined via long term immersion studies by measuring the cumulative amount of hydrogen (H2) that is emitted by samples. The cumulative H2 measurements have a direct correlation to the mass loss that the Mg alloy samples undergo during the duration of the tests. The results of the current in vitro corrosion studies are compared to 52 week small animal studies to develop predictive models for designing future biomedical devices.INTRODUCTIONBone trauma, including fracture and osteoporosis, is a major challenge for biomedical engineering. There are about 6 million bone fractures reported in the US annually with a significant number requiring some type of fixation device to facilitate healing. The majority of fixation devices are made of conventional implantable metals like unalloyed titanium (Ti), Ti alloys or stainless steel. However, a significant portion of these non-degradable implants require secondary removal surgeries which are painful and costly; but also risk infections and further fractures. In addition to the implant being permanent, post surgical complications as a result of local tissue reaction and protrusion have been recorded.
Käfer, Sven (Technische Universität Darmstadt Research Group for System Reliability) | Melz, Tobias (Technische Universität Darmstadt Research Group for System Reliability) | Kaufmann, Heinz (Fraunhofer Institute for Structural Durability and System Reliability LBF) | Engler, Christopher Tom (Technische Universität Darmstadt State Material Testing Institute and Institute for Materials Technology) | Anderson, Georg (Technische Universität Darmstadt State Material Testing Institute and Institute for Materials Technology) | Oechsner, Matthias (Technische Universität Darmstadt State Material Testing Institute and Institute for Materials Technology)
ABSTRACTEngine components, such as injection systems, encounter a large number of load cycles (N > 107) during their lifetime and are exposed to potentially corrosive media such as fossil fuels. For this reason, corrosion fatigue in the very high cycle fatigue (VHCF) regime has to be taken into account for reliable fatigue design. To reduce carbon dioxide (CO2) emission, fossil fuels are blended with biogenic components. Biofuels are potentially more corrosive than unblended fuels due to the hygroscopic properties, e.g. ethanol, which is added to gasoline fuels.There is not much known about the corrosion fatigue behavior of high-strength chromium steels in bio-fuels, yet. Indeed investigations show that biofuels reduce the number of load cycles to failure of engine components significantly . Therefore, it is essential to investigate the corrosive impact of fuels with biogenic components by performing corrosion fatigue tests. In the current paper, the impact of corrosion fatigue was investigated on notched and unnotched specimens of stainless 17% chromium steel 1.4016 (X6Cr17), AISI 430 in air and E85 biofuel (gasoline fuel with 85% ethanol added). The results were obtained at a stress ratio of R = 0 with different testing rigs to investigate the influence of testing frequencies (f = 20, 150Hz). The test results represent the basis for a concept that will be able to estimate the impact of corrosion fatigue in the VHCF region.INTRODUCTIONThe amount of renewable sources shall be increased to 10% in biofuels according to the directive 2009/28/EC  to reduce the greenhouse gas emissions in 2020 by 6% . During the implementation of E10 biofuel, many consumers have been averse to biofuels, because of the lack of long-term studies in conventional combustion engines . Due to the higher amount of ethanol, the hygroscopic properties of biofuels increase causing an input of different kinds of corrosive substances, e.g. chlorides that are dissolved in water. High alloyed Cr-steels that are used in engine components form passive layers protecting the core material from further corrosion. High chloride contents superimposed by mechanical load can locally damage these passive layers resulting in pitting and possibly intergranular corrosion. These effects have a major impact on the fatigue strength of the materials . The corrosive impact occurs most of the time at the high stressed part of engine components at the surface. This results in a superimposed crack initiation and crack propagation. Therefore, corrosive fatigue tests results are of great interest for such components. Regarding the downsizing trend of the automotive industry by reducing fuel consumption and simultaneously increasing the engine power in terms of material optimization, it is indispensable to consider the effect of corrosion already in an early stage of development. For this reason, corrosion fatigue effects have also to be taken into account during the design process of engine components such as fuel pumps, the fuel distributors, and high-pressure injection valves  by choosing the right material and the right design.
ABSTRACTThis study focuses on a better understanding of pitting and crevice corrosion on coating surface damaged carbon steels in automotive applications. Immersion and cyclic polarization tests were conducted on bare and coated metals in a 5% NaCl solution. The morphology of localized corrosion, including a filiform appearance, was characterized after exposure to the corrosive environment. To simulate the coating damage of automotive suspension coil springs and stabilizer bars under road conditions, a sharp-tipped scratching awl was used to create scratches and indents. Localized corrosion on the zinc phosphate (ZnP) pretreated and coating damaged surface was investigated in a 24-hour immersion test. The correlation between localized corrosion and metal substrate exposure is studied. Key factors affecting the localized corrosion of carbon steels with damaged coating are discussed.INTRODUCTIONCarbon steels are widely used in automobiles to achieve the desired strength of components and to maintain a lower cost than other materials. However, the corrosion of carbon steel caused by road salts and emissions was a major problem during the early years of the automotive industry. The exposure of carbon steel to a humid environment quickly generates severe corrosion on the entire exposed area. Later, the corrosion problem in the automotive industry was significantly improved by the development of coating technologies. 1 Nowadays, carbon steels with pretreatment and powder coatings are being used for many automotive applications, taking into account the balance between mechanical properties and the cost of materials and manufacturing. Leidheiser, Jr. 2 systematically summarized the problem of corrosion on painted metals and pointed out that many problems remain unsolved. Y. Ashida 3 reported a significant pitting corrosion problem from coating damaged locations, especially on the coil springs of the automotive suspension system. In order to prevent the corrosion of automotive components, it is critical to understand the mechanism of localized corrosion under imperfect coating or damaged coating conditions.
ABSTRACTSusceptibility to cracking in sour service is usually determined by testing in laboratory or simulated service environments, in compliance with NACE MR0175 / ISO 151561. Typically small scale specimens are extracted from sampled material to facilitate uniaxial tensile, C-ring or 4-point bend testing to determine the resistance to Sulfide Stress Cracking (SSC) or Stress Corrosion Cracking (SCC). Sampling relaxes residual stress and in many cases the specimen is not representative of the material surface condition and microstructure, and clearly may not represent material with inhomogeneous properties. This is particularly true for subsea lines installed by reeling as strain history varies around the entire circumference. A full ring ovalization test method was developed in the 1980s / 1990s, which retains the residual stresses, is better able to assess behavior with hoop stress and is still favored today (BS 87012), but it does not load the entire specimen. This paper describes a new axially loaded full ring test method which was developed and demonstrated to combine the benefits of retaining a full as-welded pipe pup-piece, permitting single-sided exposure, with the advantage of tensile loading of the complete tubular specimen.INTRODUCTIONCarbon steel girth welds for sour service applications are typically qualified using either small-scale four point bent beam tests, to the requirement of NACE TM01773 / EFC 164 or ‘full-scale‛ full ring tests to OTI 95 6355 (BS 87012). The four point bend test method can be un-representative of the material in service, since all faces of the specimens are exposed to the hydrogen-charging environment and the as-manufactured bore and weld root surface is often removed during the preparation operations. In addition the residual stresses from the pipe manufacture, welding and any subsequent processes are significantly reduced or removed. The ‘loss‘ of residual stresses is compensated for in NACE MR075 / ISO 151561 by applying stresses based on the actual yield strength (AYS) as opposed to the design stress, resulting in the requirement to stress specimens to 80% AYS for standard NACE TM0177- Solution A3 conditions or at 90% AYS for fitness-for-purpose conditions.
ABSTRACTSlow strain rate testing is a method that is fast and has a strong potential for ranking alloys for material selection purposes. However, it is a test method that is subject to different issues that may affect the results and lead to inconsistent conclusions. This paper demonstrates that the specimen surface morphology resulting from the final grinding of the material has an impact on the performance of the material. Longitudinal polishing is recommended to avoid the increase of crack nucleation sites by the intersection with of the slip planes that are active during plastic deformation. With regard to the testing conditions, the effect of the filling rate on the pressure and the H2S concentration in the solution at high temperature was analyzed for a given test environment. The values of the reduction in area are critical to the acceptance of the material. For this reason, the repeatability and reproducibility of this parameter as well as the uncertainty of its measurement were evaluated using the ANOVA method for different operators and types of fracture surface. Finally, special attention was paid to the characterization of the primary fracture surface and the gauge section of the tested specimens of two different corrosive-resistant alloys using scanning electron microscopy and their subsequent classification according to the NACE TM0198 standard.INTRODUCTIONThe slow strain rate test, SSRT, is a method used for screening corrosion-resistant alloys (CRA) for downhole use. In this method the specimen is exposed to a continuously increasing uniaxial tensile stress imposed by a slow and constant extension rate in the presence of an acidic aqueous environment containing H2S, CO2 and brine at an elevated temperature.1 The test conditions are usually defined by taking into account the environmental conditions in-service. The SSRT is frequently used as a quality control test due to its short duration relative to other test methods that are common to evaluate the stress corrosion cracking resistance (SCC) of high alloys such as those listed in standard NACE TM0177.2 However, issues related to specimen preparation, the reproducibility of the testing conditions, and the characterization of the tested specimens could affect the final result and lead to inconsistent conclusions.3–5 The purpose of this study is to review some of those factors and to show some interesting facts related to those factors that should to be taken into account.
Eroini, Violette (Statoil ASA) | Oehler, Mike Christian (DNV GL) | Graver, Brit Kathrine (DNV GL) | Mitchell, Anthony (Statoil ASA) | L⊘nvik, Kari (DNV GL) | Skovhus, Torben Lund (VIA University College)
ABSTRACTIncreasing incidence of amorphous deposits in both production and water injection systems has caused considerable problems for offshore oil fields. Amorphous deposits, which are a widely recognized, but often poorly explained phenomenon, are typically comprised of both organic (biological or hydrocarbons) and inorganic material, but with compositions that vary considerably. One recurrent form of deposits, found in offshore water injection flowlines and wells, consisting mainly of magnetite as the corrosion product, was further investigated with the objectives of explaining its formation and assisting in prevention or remediation. It is proposed that the deposit formation, observed in offshore water injection systems treated with nitrate, is initiated by formation of a nitrate reducing biofilm promoting under deposit corrosion by activity of sulphate reducing and methanogenic prokaryotes, this in turn generating iron hydroxide and green rusts which are then mineralized through biotic or abiotic mechanisms to magnetite. This paper reviews current observations from the offshore oil fields and presents the potential biotic and abiotic mechanisms to magnetite formation.INTRODUCTIONFouling, composed of both organic and inorganic compounds, has caused concerns within operating assets due to the detrimental effect on production and injection, in addition to challenges with intervention and integrity. The variety of deposits and poor understanding of their nature has led to confusion and sometimes inappropriate treatment. Initial work, undertaken to classify the different substances encountered, has been previously reported.1Systematic analysis allowed the development of a classification matrix intending to describe similar material in terms of their major components. The objective was to clarify confusion related to these deposits, variously described as “Schmoo” or “Black Sticky Stuff” and provide the industry with tools to help with identification and mitigation. In addition, knowledge of general formation mechanisms has been gained. A simplified version of the classification matrix is presented in Figure 1.From this study, attention was drawn on one particular form of amorphous deposit of type 1 A (corrosion products and micro-organisms) which has been regularly reported in seawater injection systems. The material is composed of biomass and the crystallized form of iron oxide - magnetite. Functional issues associated are mainly equipment impairment which threatens integrity, disruption of intervention and loss of injectivity. This paper focuses on understanding the potential mechanisms by which this offshore oilfield deposit forms, to assist prevention and mitigation.
ABSTRACTThe use of polymer based chemical inhibitors has the advantage of utilizing chemical, macromolecular, and compositional (blends or block copolymers) towards chemical inhibitors whether it is for corrosion or scaling issues. It is important to understand the multi-phase condition of production fluids whether it is extraction or circulation (oil and gas vs geothermal brine). It is also important to understand the mechanism and the long-term action of inhibition from the fluid to the surface that is being protected. This talk will highlight the principles and work in investigating various corrosion and scaling inhibitors for the production and process industries. In particular, the use of block-copolymers and hyperbranched oligomeric design in inhibitors is of a high interest because of the multi-dentate and stability (or predictability) of their solubility in various phase conditions. While a number of these examples are highlighted in the design of new materials and dosing methods, it is important to stress the cost- performance ratio of chemical inhibitors and their long term viability for continuous dosing from upstream to downstream. The work of the author also involves a number of analytical methods and testing methods that can be used to augment circulation fluids under high pressure and temperatures.INTRODUCTIONMetals in their elemental state or as pure metals (reduced) are eventually oxidized under ambient conditions except for noble metals such as Au, Pt, etc. It is an electrochemical event, the result of which is the degradation of properties if not the formation of then films of metal oxides that we call rust. The economic cost on structures, machines, vehicles, is enormous based on studies by the National Association of Corrosion Engineers (NACE) to the total to US$ 276 billion or 3.1% of the country's Gross Domestic Product (GDP). Various mitigation techniques, about US$ 121 billion is spent, a majority of which is on the use of corrosion protective coatings. These are either alarming number for most industries or create a variety of business opportunities and scientific/technical challenges. In a March 2016 NACE report, “IMPACT – the International Measures of Prevention, Application, and Economics of Corrosion Technologies,” the global cost of corrosion was estimated to reach up to US$ 2.5 trillion or approximately 3.4% of the global GDP. The cost to process, production, and transport, industries is staggering. Various protocols have be used to significantly slow down the rate of corrosion. The most common of which includes the application of protective and barrier coatings, which can employ corrosion inhibiting additives onto metal surfaces.1
ABSTRACTThis paper highlights several cases where alkaline-carbonate stress corrosion cracking (ACSCC) occurred in atypical locations, including a cold wall Fluid Catalytic Cracking (FCC) Unit regenerator, sour water stripper (SWS) pumparound piping, SWS ammonia acid gas knockout piping, and a mercaptan oxidation unit. These unusual failure locations highlight the need for a fundamental understanding of the ACSCC mechanism. This paper discusses work done to monitor on-going ACSCC risks through sour water sampling, chemical analysis, and ionic modeling.INTRODUCTIONTypically, ACSCC is associated with FCC sour water streams. While it has been recognized that ACSCC risks exist outside FCC sour water services, there have been few published cases of ACSCC in other locations. ACSCC is considered an uncommon damage mechanism that afflicts refinery equipment in a range of operating scenarios. In the 1980's and into the 1990's refineries across North America experienced severe cracking issues in FCC wet gas compression units. Damaged equipment was replaced with post-weld heat treated (PWHT) carbon steel (CS), which appears to mitigate ACSCC risk, if heat treatment was done properly.This paper includes the authors' current understanding of the ACSCC mechanism in refinery sour waters. The discussion of the mechanism is motivated by several recent examples of ACSCC outside of FCC gas recovery units. These case histories, along with the monitoring program one refinery has implemented, are presented. It is presented as a reference to evaluate process changes for potential ACSCC risk and to investigate failures of carbon steel assets in alkaline sour water service.Review of the Carbonate SCC MechanismCO2 dissolves in alkaline water to form carbonate (CO3−2) and/or bicarbonate (HCO3–) ions. Carbonates are possible above pH 8.1, while bicarbonates are soluble at pH less than 7. These ions can react with a carbon steel pipe or vessel to form a iron carbonate (FeCO3) scale as part of the active corrosion process. Eventually the system reaches a steady-state, and a reduced corrosion rate, as the scale limits species diffusion to and from the steel surface.