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Collaborating Authors
Corrosion
ABSTRACT Tribocorrosion processes of austenitic stainless steel in a medium close to that used in pressurized water reactor nuclear plants have been investigated using electrochemical impedance and noise measurements. The experiments were carried out under a steady-state friction regime yielded by the continuous circular displacement of a fretting probe against a large disk electrode. Finite-element-method simulations of the current distribution in a conventional three-electrode cell showed that a significant part of the anodic current generated by the film removal and surface repassivation at the wear track does not flow to the counter electrode and, therefore, is not measured by the potentiostat. A specific arrangement with two working electrodes, a small disk electrode inserted at the center of the large one and electrically isolated from it, was devised to monitor the anodic current induced by the tribocorrosion process. Results have shown that only a small part of the current lines flows to the central region connected through the zero-resistance ammeter. In spite of this, the power spectral density of the current fluctuations generated at the wear track could be estimated, provided that the impedances of the two working electrodes have been previously measured. The use of water-based solutions as lubricants has tended to increase following the upcoming limitations of widespread organic compounds. The presence of an electrically conductive medium in sliding contacts leads to an increase in the corrosion aggressiveness, which justifies the scientific and technological interest devoted to tribocorrosion phenomena both in laboratory and field applications during the last decade.1-5 On the other hand, the electrical conductivity of the medium brings up the opportunity of gathering in-situ information about tribocorrosion processes by means of electrochemical approaches, starting from the simple open-circuit potential monitoring to more powerful tools such as the electrochemical impedance6 and electrochemical noise techniques.7-8 In spite of this increasing interest in tribocorrosion phenomena, much work remains to be done to comprehend the kinetic mechanism and the synergetic interaction between the electrochemical and mechanical processes taking place at the interface.2,9-10 Indeed, even if it is widely accepted that the interaction between a fretting head of a sliding counterbody and the metallic surface damages the protective film, the dynamics of film rupture and repassivation are not clearly established. Some papers were then devoted to the investigation of the complex interaction between mechanical loading and film integrity. Mischler and coworkers have pro-
ABSTRACT To develop a new corrosion sensor for detecting and monitoring the external and internal corrosion damage of buried pipeline, the correlation of its output to the corrosion rate of steel pipe was evaluated by electrochemical methods in two soils of varying resistivity (5,000 ·cm, 10,000 ·cm) and synthetic tap water environments. In this paper, two types of galvanic probes were manufactured: copper-pipeline steel (Cu-CS) and stainless steel-pipeline steel (SS-CS). A comparison of the sensor output and corrosion rates revealed that a linear relationship was found between the probe current and the corrosion rates. In the soil resistivity of 5,000 ·cm and tap water environments, only the Cu-CS probe had a good linear quantitative relationship between the sensor output current and the corrosion rate of pipeline steel. In the case of 10,000 ·cm, although the SS-CS probe showed a better linear correlation than that of the Cu-CS probe, the Cu-CS probe is more suitable than the SS-CS probe because of the high current output. A correlation based on the ratio of the total charge of the pipeline/Cu-CS probe was determined as 0.39 ~ 0.41 in soil environments and 0.76 in synthetic tap water, respectively. This is an indication that the slope parameter can reflect the types of environment.
- Energy > Oil & Gas > Upstream (1.00)
- Water & Waste Management > Water Management > Water Supplies & Services (0.94)
- Materials > Metals & Mining > Steel (0.87)
ABSTRACT For economic reasons, the United Kingdom power industry is now operating its 500-MW coal-fired plants on a two-shift cycle in which the turbines are on-load for 16 h per day and off-load overnight and weekends. The concern with "two-shifting" is the impact on environment-assisted cracking of the associated transients in stress, water chemistry, and temperature.1 On-load, with well-controlled water chemistry, the condensate on the low-pressure turbines will be free of oxygen, with chloride and sulfate levels both up to about 300 ppb. Off-load, with the steam fully condensed, the condensate would tend to reflect the inlet water chemistry, with only a few ppb of chloride and of sulfate, but aerated unless there is nitrogen blanketing. The stress off-load would be zero. Ideally, to fully simulate two-shifting in laboratory testing, the combined influence of transient stress and water chemistry would be evaluated, but there are technical difficulties in synchronizing the changes in the stress, temperature, oxygen, and anion (chloride and sulfate) concentrations. For the purpose of assessing the impact of transient stress on crack propagation, the environment was held constant. In previous work using a 3NiCrMoV disc steel, a very severe environment--aerated 1.5-ppm Cl solution at 90°C2--was adopted. In the present study, a more relevant environment for the on-load simulation of de2 aerated 300 ppb Cl + 300 ppb SO4 solution at 90°C was used. EXPERIMENTAL PROCEDURES Materials The material used was a disc steel (3% NiCrMoV), cut from an ex-service steam turbine disc. The chemical composition is listed in Table 1. Specimens Compact tension (CT) specimens were made in accordance with ISO 7539-6.3 The thickness (B) and
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (0.69)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (0.69)
- Facilities Design, Construction and Operation > Processing Systems and Design > Compressors, engines and turbines (0.62)
ABSTRACT Nickel-based alloys are among the most corrosionresistant alloys in a broad range of environments. The amount of chromium and molybdenum present in the alloy has a significant effect on the corrosion properties of the metal. This study examines the influence of chromium and molybdenum on four nickel-based alloys (Table 1), including Alloy 22 (UNS N06022),(1) in various salt brines. UNS N06022 is a highly corrosion-resistant nickel-based alloy, which has a range of uses, including dental implants and in industrial settings where highly corrosive environments are encountered. In general use, Alloy 22 often comes in contact with concentrated brines at elevated temperatures. Alloy 22 was used as a standard alloy, and two ternary alloys were chosen based on the Alloy 22 composition, but with varying amounts of the primary passivating components (chromium and molybdenum). The ternary compositions were Ni-11Cr-7Mo and Ni-11Cr-13Mo. A binary alloy with 20 wt% Cr was also examined. The corrosion resistance of several Ni-Cr-Mo alloys have been discussed in detail.1 In brief summary, Alloys C (UNS N06003), C-276 (UNS N10276), C-4 (UNS N06455), and Inconel Alloy 625 (UNS N06625) have been tested for corrosion resistance in acidic solutions, including hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), hydrofluoric acid (HF), and phosphoric acid (H3PO4). The alloys with higher molybdenum content usually show the best resistance to reducing environments such as H2SO4 and HCl and pitting attacks from chloride-containing solutions, while the alloys with higher chromium content usually have the best resistance to strongly oxidizing solutions such as HNO3.
- Materials > Metals & Mining > Nickel (1.00)
- Materials > Chemicals > Commodity Chemicals (0.88)
- 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 Carbon dioxide (CO2) corrosion has become one of the most serious corrosion types of oil well tubular goods, which has induced a large amount of economic loss and calamity. Many investigations show that ferrous carbonate (FeCO3) is the basic composition in the corrosion product scale on the steel substrates in saturated and nonsaturated CO2 solution containing oil. Whether or not the scale can protect the substrate from CO2 corrosion depends on its physical characteristics.1 The complete, close-grained, and more adhesive protecting scale can decrease the corrosion rate. The physical characteristic of the scale is closely related to its forming conditions. Temperature and CO2 pressure are two of the important external factors in the CO2 corrosion process. Schmitt2 considered that there is an intrinsic change in the kinetics in the CO2 corrosion process around 60°C. Many investigators2-5 also observed the following: --Uniform corrosion takes place on the surface of a ferroalloy below 60°C. --The corrosion product scale is a noncompact, soft, and nonadhesive ferric carbonate. --The surface of the substrate is smooth. --There is a transitional range between 60°C and 110°C, in which the ferroalloy could produce the scale with a certain protecting property and evident local corrosion. --Around 110°C, the uniform corrosion rate is high, local corrosion is serious, and the scale contains thick crystals.
ABSTRACT The oil industry contains a wide variety of corrosive environments. Mexican crude oil and gas commonly contain entrained water, carbon dioxide (CO2), and hydrogen sulfide (H2S). The transport of these types of products always induces failures in the pipeline systems, and not less frequently in the weld beads. The welding industry has recognized that weldinduced stresses play an important role in certain localized corrosion phenomena. Each year, tens of million of dollars are expended to replace or repair pipes and vessels that suffer excessive localized metal loss, stress corrosion cracking (SCC), or hydrogen embrittlement (HE). When sulfide is present, this type of brittle failure is known as sulfide stress cracking (SSC), and it has been established as a particular case of HE. Weld metal corrosion is normally attributed to the differences in composition and to differences in electrochemical potentials between the parent metal, heat-affected zone (HAZ), and weld metal. A lower electrochemical potential of the weld bead is commonly related to the composition, microstructure, and distribution of inclusions.1 The suitable sour service materials are listed in NACE MR0175,2 whereas the TM01773 lists Method A as one of the tests to be performed to determine the inclusion of a material in MR0175. Many highstrength, low-alloy steels are precluded from undergoing this test, especially in the as-welded condition, due to either high parent material hardness or the formation of high-localized stressed weld regions in the weld HAZ. Specifications for welded sample testing are not addressed in the NACE standard primarily because this test is geared toward wrought samples. Welded samples differ from homogeneous samples because of their local variations in microstructure and
- 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 Hydrogen cracking associated with alloys used in harsh marine conditions often occurs without any warning or changes in surface appearance and results in sudden in-service failure. Cathodic protection (CP) is often used with marine alloys in an effort to prevent corrosion of the ship's structure. The application of the cathodic potential promotes hydrogen generation that causes an increased risk of hydrogen-assisted cracking from the hydrogen diffusion in the material.1-3 Because of this possibility, many studies have been carried out related to hydrogen accumulation in metallic alloys that have been cathodically charged. The majority of these studies were performed in ferritic (body-centered cubic [bcc]) alloys, which are known to be more susceptible to hydrogen cracking than austenitic (face-centered cubic [fcc]) alloys. However, hydrogen-assisted cracking in austenitic alloys has been reported.4-5 The alloy, UNS N05500,(1) used in this investigation, is known to be highly corrosion resistant in harsh marine conditions. UNS N05500 is an agehardenable, nickel-copper alloy that combines excellent corrosion resistance with great strength and hardness. Its uses include marine shafts and equipment, valve seats, springs, gears, and pulp scraper blades and fasteners. It has been found that hydrogen-assisted cracking induced by CP can occur not only in steel6-7 but also during cathodic charging of corrosion-resistant austenitic alloys, i.e., nickelcopper alloy parts under CP.
ABSTRACT Mild steel is an inexpensive pipeline construction material frequently used in the oil and gas production and transportation industry; however, it is not inherently resistant to internal corrosion in the presence of carbon dioxide (CO2), hydrogen sulfide (H2S), organic acids, etc. It may be used safely in some cases when protective corrosion films form such as iron carbonate (FeCO3). FeCO3 is a by-product of CO2 corrosion and may be deposited on the parent material. It slows down further corrosion by presenting a physical barrier that retards diffusion of corrosive species and by blocking the steel surface.1 Therefore, any damage to this film is typically followed by a severe corrosive attack and may ultimately lead to costly equipment failure.2 Even though the exact mechanism of the film removal is still not well understood, the removal phenomenon in single-phase aqueous flow is commonly attributed to one or a combination of the two mechanisms: --mechanical film removal by hydrodynamic forces,3-6 and/or --chemical film dissolution, which is believed to be governed by mass transfer.7-9 There are numerous studies of the hydrodynamics of turbulent flows and the impact on mechanical film removal. In some initial work, a commonly used parameter used as a criterion for the onset of mechanical removal was the critical or breakaway velocity.10-12 However, this concept lacked universality and could not be used in different flow geometries.13 Efird introduced the critical wall shear stress as the
- 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 Crack growth rate (CGR) measurement is an important tool to understand the behaviors of environmentally assisted cracking (EAC) of various materials used in light water reactor (LWR) environments and to produce quantitative data for structural integrity analyses, as well as for dispositioning existing or postulated defects. In this paper, the results of corrosion fatigue (CF) and stress corrosion cracking (SCC) experiments with two different reactor pressure vessel (RPV) steels at 288°C (~561 K) under simulated boiling water reactor (BWR) conditions are presented. CGR was found to be dependent upon various mechanical factors such as the stress intensity factor range (K), loading frequency, and hold time (tH) at maximum load. In CF tests, it was observed that whether the loading frequency was high or low, the fatigue crack growth rate (FCGR) increased as K increased under the same water quality and loading conditions. In SCC tests, the longer the tH, the slower the CGR. On the other hand, it was found that dissolved hydrogen (DH), which lowered the electrochemical potential (ECP), could significantly decrease the CGR in either CF or SCC tests. The steel sulfur content had little effect on FCGR under low-frequency loading and low-flow, oxidizing BWR/normal water chemistry (NWC) conditions. CGR data from this study were comparable with those predicted by some well-known CGR models for oxidiz In the early 1970s, Kondo, et al.,1 first reported an adverse influence of high-temperature (260°C) water on the fatigue crack growth rates (FCGR) of low-alloy steels (LAS). Thereafter, many significant investigations worldwide have been focused on this phenomenon--the so-called environmentally assisted cracking (EAC) of LAS in simulated boiling water reactor (BWR) conditions.2-11 The EAC growth rate in pressure boundary components in water-cooled nuclear power plants--for instance, the reactor pressure vessel (RPV)--is one of the most important parameters relating to reactor safety evaluation, in-service inspection, and lifetime prediction. For LAS, such as A508 Cl.2 (UNS K12766)(1) and A533B (UNS K12539), EAC can occur in one of the three forms: corrosion fatigue (CF),12-30 strain-induced corrosion cracking (SICC),31-35 and stress corrosion cracking (SCC).36-52 The first two forms occur under cyclic or transient load, e.g., due to startup, shut
- North America > United States (1.00)
- Europe (0.93)
- Geology > Mineral (0.68)
- Geology > Geological Subdiscipline > Geomechanics (0.48)
- 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)
- Health, Safety, Environment & Sustainability > Environment (0.88)
ABSTRACT Corrosion tests were conducted to select the structural material for a reactor to decompose organic wastes generated from nuclear power plants, utilizing the supercritical water oxidation (SCWO) process. Test conditions were based on the decomposition of chloroprene (C4H5Cl) and cation exchange resin, which generate hydrochloric acid (HCl) and sulfuric acid (H2SO4) in process fluids. In order to select candidate materials, short-period screening tests were carried out on various corrosion-resistant materials in HCl and H2SO4 solutions, using static test vessels at 300°C, 400°C, and 450°C. Subsequently, cyclic corrosion tests were carried out for Ta, Ti, and Ti alloys to estimate the corrosion rate and to evaluate their applicability for waste-processing plants. The results of these tests indicate that the corrosion resistance of Ti alloys is sufficient for them to be applied as reactor materials for organic waste decomposition systems using the SCWO process. In this paper, the stability of surface films is discussed using potential-pH diagrams and oxide film analyses. Based on the test results, a bench scale, flow-through-type test reactor
- Asia > Japan (0.69)
- North America > United States (0.47)
- 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)
- Health, Safety, Environment & Sustainability > Environment > Waste management (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)