Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (52)
- Beitrag zu einem Tagungsband (38)
- Beitrag zu einem Sammelband (12)
- Vortrag (6)
- Posterpräsentation (4)
- Forschungsbericht (1)
Schlagworte
- Corrosion (44)
- CCS (41)
- Steel (35)
- CO2-storage (18)
- Pipeline (17)
- High temperature corrosion (12)
- CO2-injection (9)
- Heat treatment (8)
- Supercritical CO2 (7)
- Aquifer (6)
Organisationseinheit der BAM
- 5 Werkstofftechnik (39)
- 5.1 Mikrostruktur Design und Degradation (39)
- 7 Bauwerkssicherheit (6)
- 7.6 Korrosion und Korrosionsschutz (6)
- 5.6 Glas (2)
- 8 Zerstörungsfreie Prüfung (2)
- 8.0 Abteilungsleitung und andere (2)
- 4 Material und Umwelt (1)
- 4.2 Material-Mikrobiom Wechselwirkungen (1)
- 5.2 Metallische Hochtemperaturwerkstoffe (1)
Eingeladener Vortrag
- nein (6)
Unusual Corrosion Behavior of 1.4542 Exposed a Laboratory Saline Aquifer Water CCS-Environment
(2017)
Differently heat treated coupons of 1.4542 were kept at T=60 °C and ambient pressure as well as p=100 bar for 700 h - 8000 h in an a) water saturated supercritical CO2 and b) CO2-saturated synthetic aquifer environment similar to on-shore CCS-sites in the Northern German Basin. Surface corrosion layers are homogeneous but unusually discontinuously ellipsoidal. After 8000 h at 100 bar maximum corrosion rate in the liquid phase is approximately 0.014 mm/year, with normalizing providing best corrosion resistance and approximately 0.003 mm/year in the supercritical phase where hardening+tempering at 670 °C leads to lowest corrosion rates.
To mitigate carbon dioxide emissions CO2 is compressed and sequestrated into deep geological layers (Carbon Capture and Storage CCS). The corrosion of injection pipe steels is induced when the metal is in contact with CO2 and at the same time the geological saline formation water. Stainless steels X35CrMo17 and X5CrNiCuNb16-4 with approximately 17% Cr show potential as injection pipes to engineer the Northern German Basin geological onshore CCS-site. Static laboratory experiments (T = 60 ◦C, p = 100 bar, 700–8000 h exposure time, aquifer water, CO2-flow rate of 9 L/h) were conducted to evaluate corrosion kinetics. The anomalous surface corrosion phenomena were found to be independent of heat treatment prior to exposure. The corrosion process is described as a function of the atmosphere and diffusion process of ionic species to explain the precipitation mechanism and better estimate the reliability of these particular steels in a downhole CCS environment.
Thin Sol-Gel Alumina Coating as Protection of a 9% Cr Steel Against Flue Gas Corrosion at 650 °C
(2018)
Samples of sol-gel alumina coated and uncoated P92 steel were exposed to flue gas at 650 °C for 300 h. As result of this treatment a 50 µm thick bi-layered oxide scale had formed on the surface of the uncoated sample. Below the scale a 40 µm thick inner oxidation zone was detected. In contrast, the porous, micron thick alumina coating enabled the formation of a chromium oxide scale with a thickness of some nanometers at the interface between steel substrate and coating. In this case high temperature corrosion of the steel was prevented so far.
Corrosion fatigue specimen with different surfaces (technical surfaces after machining and polished surfaces) of high alloyed martensitic stainless steel X46Cr13 (1.4043) and duplex stai nless steel X2CrNiMoN22 3 2 (1.4462) were compared at load amplitudes from 175 MPa to 325 MPa in the geothermal brine of the N orthern German Basin at 98 °C. Surface corrosion layers and pits reveal carbonate corrosion products on the surface such as FeCO 3 and FeOOH as the main precipitation phases with no dependence on the original surface roughness . At high stress amplitudes above 275 MPa technical surfaces (P50% at σa 300 MPa=5 × 10 5 ) resulted in more cycles to failure than polished (P50% at σa 300 MPa=1.5 × 10 5 ). The greater slope coefficient for technical surfaces k = 19.006 compared to polished surfaces k =8.78 demonstrate s earlier failure at given stress amplitude σa .
Coupons of X5CrNiCuNb16-4 that may be used as injection pipe with 16% Chromium and 0.05% Carbon (1.4542, AISI 630) were exposed for 3000 h to CO2-saturated saline aquifer water similar to the conditions in the Northern German Basin at ambient pressure and 60 °C. Surface corrosion layers and pits reveal carbonate corrosion products on the surface such as FeCO3 and FeOOH as the main precipitation phases with no dependence on the original surface roughness. Corrosion rates for polished and technical surfaces were below 0.005 mm/year compared to corrosion rates of 0.035 mm/year after shot peening.
Properties of pipe steels for CCS technology require resistance against the corrosive environment of a potential CCS-site (heat, pressure, salinity of the aquifer, CO2-partial pressure). The influence of austenitizing in heat treatment routines of two different injection pipe steels (1.4034, X46Cr13 and 1.4021, X20Cr13) was evaluated. Steel coupons were austenitized at different temperatures (900 – 1050 °C) for different lengths of time (30–90 min) before quenching and annealing prior to long term corrosion experiments (60°C, 100 bar, artificial brine close to a CCS-site in the Northern German Basin, Germany). In general, fewer pits are found on X46Cr13. Comparing steels with 13% chromium each the higher carbon content of X46Cr13 (0.46% C) results in a lower number of pits compared to X20Cr13 (0.20% C). It is found that neither the carbon content of the steels nor austenitizing temperature has much influence, but local corrosion behaviour is most susceptible towards austenitizing time
The Ni-Cr-Mo-W alloy is characterized by the excellent high-temperature corrosion resistance, good strength and ability to work in aggressive environments. To protect the surface of the substrate 13CrMo4-5 steel against aggressive environments the Inconel 686 as clad layer was used. The corrosion process was performed in oxidizing mixture of gases like O2, COx, SOx. The second part of corrosion Experiment concerned the corrosion test of the coating in reducing atmosphere of the specified gases with ashes, which contained e.g. Na, Cl, Ca, Si, C, Fe, Al.
This work presents the microstructure and chemical composition of oxide scales created on Ni – base coating after corrosion experiments in aggressive gases and ashes. The Inconel 686 coating applied on the low carbon steel 13CrMo4-5 was performed by a CO2 laser cladding process. The experiments were carried out in oxidizing gas atmospheres containing O2, COx, SOx. The second Variation of corrosion experiments were performed in a reducing atmosphere with ashes containing elements such as: Na, Cl, Ca, Si, C, Fe, Al etc. After 240 h and 1.000 h corrosion experiments the oxide scales on the substrate and overlay were created in both cases.
The sulfur compounds were found on the top of the coating surface (EPMA) and also higher contents of silica compounds were revealed on specimens covered by ashes during the experiments. The microstructure and chemical composition of the clad and scales were investigated by means of a light microscope and an electron microscope (SEM)equipped with an EDS detector.
Comprehensive insights into the early stages of corrosion mechanisms provide fundamental knowledge to further understand and model long time material behaviour. The present work studies the early stages of combined oxidation and sulphidation of ferritic model alloys for time scales up to 250 h at 650 °C to observe the influence of chromium during the corrosion under SO2. Model alloys were used to focus on the reaction of the intended elements: Fe, Cr, S, and O. Pure iron simultaneously forms magnetite and iron sulphide in an early stage of corrosion, covered by a pure oxide layer after 100 h. Iron with 13 wt% Cr shows hematite and mixed Fe-Cr-oxides first, before sulphides nucleate in the inner corrosion zone. With increasing ageing time a magnetite layer is observed below the hematite layer. Quantitative phase fractions of all corrosion products observed were determined from cross section images. Characterization of the Fe13Cr corrosion scale by FIB revealed a highly porous structure in the inner corrosion zone where Cr-rich (Fe, Cr)-sulphides are present, and caused the scale to spall easily.
Basic research on the corrosive effect of flue gases has been performed at the BAM Federal Institute for Materials Research and Testing (Germany). Conditions at both high and low temperatures were simulated in specially designed experiments. Carburization occured in flue gases with high CO2 content and temperatures higher than 500 °C. In SO2 containing flue gases sulphur was detected in the oxide scale. At lower temperatures no corrosion was observed when gases with low humidity were investigated. Humidity higher than 1500 ppm was corrosive and all steels with Cr contents lower than 12% revealed corroded surfaces. At low temperatures below 10 °C a mixture of sulphuric and nitric acid condensed on metal surfaces. Acid condensation caused severe corrosion. Humidity, CO2, O2, and SO2 contents are the important factors determining corrosion. Below 300 °C acid condensation is the primary reason for corrosion. Low humidity and low temperatures are conditions which can be expected in the CO2 separation and treatment process. This work includes major conditions of the flue gas and CO2 stream in CCS plants and CCS technology.
Der Klimaschutz erfordert die Reduzierung des Ausstoßes von Kohlendioxid. Neue Kraftwerke mit Sauerstoffverbrennung und möglicherweise CO2-Abscheidung sollen eine Reduktion des CO2 im Bereich der Energietechnik ermöglichen. Die heute üblichen Hochtemperaturwerkstoffe werden anderen Umgebungsbedingungen ausgesetzt, und es sind andere Korrosionsraten und Korrosionsreaktionen zu erwarten. In diesem Beitrag werden die Kraftwerkstechnologien kurz vorgestellt und an einem Beispiel erläutert, dass die Oxidation an Luft mit der Oxidation in Wasser nicht direkt vergleichbar ist.
The CCS technique involves the compression of emission gasses in deep geological layers. To guarantee the safety of the site, C02-corrosion of the injection pipe steels has to be given special attention when engineering CCSsites. To get to know the corrosion behaviour samples of the heat treated Steel 1.72252CrMo4, used for casing, and the stainless injection-pipe Steel 1.4034 X46Cr 13 were kept at T=60 °C and ambient pressure as well as p=100 bar for 700 h - 8000 h in a C02-saturated synthetic aquifer environment similar to possible geological on-shore CCS-sites in the northern German Basin. The isothermal corrosion behaviour obtained by mass gain of the steels in the gas phase, the liquid phase and the intermediate phase gives surface corrosion rates around 0.1 to 0.8 mm/year at ambient pressure and much lower about 0.02 to 0.2 mm/year at 100 bar where the C02 is in its supercritical state. Severe pit corrosion with pit heights around 4.5 mm are only located on the 42CrMo4 Steel. Main phase of the continuous complicated multi-layered carbonate/oxide structure is siderite FeCO} in both types of Steel.
The CCS technique involves the compression of emission gasses in deep geological layers. To guarantee the safety of the site, CC>2-corrosion of the injection pipe steels has to be given special attention when engineering CCS-sites. To get to know the corrosion behaviour samples of the heat treated Steel 1.72252CrMo4, used for casing, and the stainless injection-pipe Steel 1.4034 X46Crl3 were kept at T=60 °C and ambient pressure as well as p=100 bar for 700 h - 8000 h in a CC>2-saturated synthetic aquifer environment similar to possible geological onshore CCS-sites in the northern German Basin. The isothermal corrosion behaviour obtained by mass gain of the steels in the gas phase, the liquid phase and the intermediate phase gives surface corrosion rates around 0.1 to 0.8 mm/year at ambient pressure and much lower about 0.02 to 0.2 mm/year at 100 bar where the CO2 is in its supercritical state. Severe pit corrosion with pit heights around 4.5 mm are only located on the 42CrMo4 Steel. Main phase of the continuous complicated multi-layered carbonate/oxide structure is siderite FeCCh in both types of Steel.
Dealing with first corrosion screening experiments to predict the reliability and safety of Germanys first Carbon Capture and Storage site in the northern Bassin of Germany, northwest of the Capital Berlin, laboratory experiments have been established to simulate the particular conditions at T=60 °C, highly saline aquifer water similar to 'Stuttgart Aquifer', but only at ambient pressure. With mounting 2 independent full 2-grade titanium autoclave systems (running up to 250 bar and 300 °C) pressures up to p=100 bar are possible. In 2010 a specific corrosion chamber of 2-grade titanium working up to 100 °C, flowing aqui fer water with different gas mixtures was designed to fit to a high cycle fatigue testing machine. Long term fatigue experiments simulating fatigue crack growth under corrosive environments will soon start. These experiments may not only help engineering a CCS site, but results can be used to improve the maintenance of geothermal energy production sites, especially moved parts such as pumps and shafts.
The combustion of coal in CO2-reduced Oxyfuel power plants requires creep resistant and corrosion
resistant materials, which can withstand high temperatures up to 600°C and CO2 rich atmospheres.
Among the heat resistant materials, the 9-12% chromium steels are proven to resist high wall
temperatures in conventional power plants and are suitable as membrane wall, superheaters and steam
piping.
During Oxyfuel combustion a flue gas is generated, which consists mainly of H2O (30 mol %) and
CO2 (70 mol %). The present paper is focused on the corrosion of 9-12% chromium steels under
oxyfuel conditions in a temperature range between 550 and 625°C.
Depending on Chromium content of the 9-12%chromium steels, carburization of the base material,
perlite formation and carbide formation were observed. Alloys with lower chromium content form a
non protective oxide scale with perlite at the scale-alloy interface. Steels with 12% chromium have a
small growing oxide scale with enlarged M23C6-particles at the scale-alloy interface. The carburization
of the base material is found to be increased for the 9% Cr-steel. Higher pressure of the flue gas results
in the formation of less resistant scales and cause accelerated carburization of the base materials.
However, the carburization has an impact on the mechanical properties at the surface and leads to an
embrittlement, which is deleterious during thermal cycling.
Oxidation kinetics, phase analysis of the scale (transmission electron microscope) and carburization
depths (microprobe) of the base materials are presented.
In coal-fired power plants using oxyfuel combustion process with carbon capture and sequestration, instead of air, a mixture of oxygen and recirculated flue gas is injected in the boiler. A series of steels were exposed to CO2-SO2-Ar-H2O gas mixtures at 600 °C for 1000 h to compare their high temperature corrosion behavior. During the corrosion process, carburization, decarburization and recrystallization were observed underneath the oxide scale depending on the gas mixture and alloy composition. The conditions that lead to carburization are not yet completely understood, but decarburization can be simulated using thermodynamic and kinetic models. In this work, the results of these simulations are compared with measured values for one of the alloys that displayed a decarburized region. Since the mobility of carbon in the scale is not known, two strategies were adopted: simulation of alloy-atmosphere contact; and estimation of the carbon flux to produce the observed decarburization. The second approach might give an insight on how permeable to carbon the scale is.
In coal-fired power plants using oxyfuel combustion process with carbon capture and sequestration, instead of air, a mixture of oxygen and recirculated flue gas is injected in the boiler. A series of steels were exposed to CO2-SO2-Ar-H2O gas mixtures at 600 °C for 1000 h to compare their high temperature corrosion behavior. During the corrosion process, carburization, decarburization and recrystallization were observed underneath the oxide scale depending on the gas mixture and alloy composition. The conditions that lead to carburization are not yet completely understood, but decarburization can be simulated using thermodynamic and kinetic models. In this work, the results of these simulations are compared with measured values for one of the alloys that displayed a decarburized region. Since the mobility of carbon in the scale is not known, two strategies were adopted: simulation of alloy-atmosphere contact; and estimation of the carbon flux to produce the observed decarburization. The second approach might give an insight on how permeable to carbon the scale is.
During the compression of emission gasses into deep geological layers (Carbon Dioxide Capture and Storage, CCS) CO2-corrosion will become a relevant safety issue. The reliability of the steels used at a geological onshore CCS-site in the Northern German Bassin 42CrMo4 (1.7225, AISI 4140) used for casing, and the injection pipe steels X46Cr13 (1.4034, AISI 420 C), X20Cr13 (1.4021, AISI 420 J) as well as X35CrMo17 (1.4122) is demonstrated in laboratory experiments. Samples were kept in a synthetic aquifer environment at T = 60 °C. This corrosive environment is then saturated with technical CO2 at a flow rate of 3 l/h. Microstructures were characterized by X-ray diffraction, light microscopy, scanning electron microscopy, and energy dispersive X-ray analysis, after a series of heat treatments (700 h to 2 years). The non-linear isothermal surface corrosion behaviour of the steels reveals surface corrosion rates around 0.10.8 mm/year, when obtained by mass gain. Severe pit corrosion (pit heights ca. 4.5 mm) are only located on the injection pipe steels. Main phases of the continuous scales are siderite FeCO3 and goethite α-FeOOH. The formation of the non-protective layer is likely to form via a
transient Fe(OH)2-phase.