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Eingeladener Vortrag
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The screening of coatings shows that the modification by adding individual pigment was not sufficient to protect carbon steel even during a short-term exposure, indicated by the discoloration after only seven days of exposure.
Electrochemical tests indicated that the coating cathodically protects carbon steel or slows down the corrosion reaction.
A long-term exposure test confirmed that the PANI/SiO2 modified coating successfully protects the carbon steel in the Sibayak artificial geothermal water at 150 °C for 6 months.
Corrosive geothermal brines are a major challenge to geothermal power-plants. For cost reasons, plant designers favorize low alloyed steels, e.g., carbon steel, which are susceptible to uniform and localized corrosion when exposed to geothermal brines having acidic and saline properties. To solve such problem, coatings or inhibitors would be a protective solution as an alternative to the use of high alloyed materials.
This study investigated a coating system consisting of polyaniline/silicon dioxide basing on locally available resources. Protection against corrosion of carbon steel is shown by long-term exposure and electrochemical tests of coated carbon steels, performed in an artificial acidic and saline geothermal brine, comparable to real conditions at a site in Indonesia.
Therefore, an integrated coating system is presented for corrosion protection, combining the electro-chemical functionality of polyaniline and the physical advantages of silica.
Nachdem im Verbundprojekt COORAL das Hauptaugenmerk auf überkritisches CO2 gelegt wurde, d. h. Transport über kurze Strecken bei erhöhter Temperatur, wurde in CLUSTER ein größeres lokales Transport-Netzwerk betrachtet, bei dem CO2 bei geringeren Temperaturen, also vorwiegend im flüssigen Zustand transportiert wird. Wurden in COORAL die CO2-Ströme von Kohlekraftwerken untersucht, ging es in CLUSTER zusätzlich um die Emissionen von relevanten Industrien, deren CO2-Emissionen nicht ohne Weiteres vermieden werden können.
Aufgrund der Erfahrungen in COORAL konnte eine Auswahl von kommerziellen Werkstoffen getroffen werden, die für einen konkreten Einsatz für CCS zur Verfügung stünden. Die gemischten und fluktuierenden CO2-Zusammensetzungen sind bei geeigneten Begrenzungen der Begleit¬stoffe im CO2 bezüglich Korrosionsvorgänge beherrschbar. Die Machbarkeit eines lokalen CCS-Clusters erscheint daher gegeben, soweit dies die Anlagen für Kompression, Transport und Injektion betrifft.
This book fulfills its intention to provide a comprehensive overview on 3D-printing of metals.
The interested reader can get a lot of information about the topics one should deal with when working with additively manufactured metallic parts. It gives a general roadmap where to start, what to learn and how it fits together.
This book provides a state‐of‐the‐art overview on the processing, characterization, and modelling of metallic and ceramic materials used for energy and environmental applications. 17 scientists show a collection of current knowledge in 8 chapters.
This book fulfills its intention to provide a reference book containing a collection of publications on thin films and coatings made of ceramic and metals used for energy and environmental applications. It covers a broad range of this topic and provides a comprehensive insight. Graduate and undergraduate students of materials science and mechanical engineering can find an overview on this topic to step in this interesting field of engineering.
Aging of passive film formed on UNS N08031 was investigated as a function of passivation time in Green-Death solution at 40°C. The specimen surface was in a stable passive state in the solution.
The passive current density increased with an increase in the passivation potential. Electrochemical Impedance Spectroscopy and Mott–Schottky (M–S) analyses revealed that a more defective n-type
semiconductive passive film formed as the potential increased while the film became stable as the defects in the film decreased at potential lower than 1.0 VSSE. The increase of the applied potential and the polarisation time are likely reasons for the change in passive film stability.
Im ISO/TC 265 werden Normen zur Entwicklung, Konstruktion, Betrieb, Umweltplanung und -Management, Risikomanagement, Quantifizierung, Monitoring und Verifizierung sowie weitere Aktivitäten für die einzelnen Stufen der CCS-Prozesskette erstellt.
Als neuer Aspekt wurde die Zusammensetzung des CO2-Stroms angesprochen. In Form eines "State-of-the-Art-Reports" soll der derzeitige Kenntnisstand zusammengestellt werden. Dieses soll für einen späteren Normenentwurf als Grundlage dienen.
BAM, IKS Dresden und ThyssenKrupp VDM haben ein umfangreiches Versuchsprogramm mit geschweißten Werkstoffprüfblechen durchgeführt, um neue Erkenntnisse über das Korrosionsverhalten der Superaustenite und der Nickelbasislegierung zu gewinnen und um diese Bewertungen im Abschnitt 5 der BAM-Liste zu berücksichtigen. Das Versuchsprogramm umfasste Korrosionsbeständigkeitsbewertungen der drei höherlegierten Werkstoffe in Stoffen aus 12 Gruppen von korrosiven Gefahrgütern, wie z. B. anorganische Halogenide, organische Säurehalogenide, Halogencarbonsäuren, Chlorsilane, Chlorate, Perchlorate, Chlorite, Hypochlorite, Hydrogensulfate und Nitriersäuren.
In der DIN 6601 - Beständigkeit der Werkstoffe von Behältern/Tanks aus Stahl gegenüber Flüssigkeiten (Positiv-Flüssigkeitsliste) ist die Beständigkeit unlegierter Stähle, austenitischer CrNi- und CrNiMo-Stähle gegenüber den reinen Ottokraftstoffen bewertet. Mit der verstärkten Verwendung bioethanol- und biodieselhaltiger Kraftstoffe und Heizöl stellt sich auch die Frage nach der Beständigkeit der handelsüblichen Tank- und Behälterwerkstoffe sowie der Dichtungswerkstoffe unter dem Einfluss dieser Medien.
Comparison of the corrosion resistance to dangerous goods of austenitic CrNiMo and duplex steels
(2014)
The “BAM-List - Requirements for Tanks for the Transport of Dangerous Goods” is the basis in Germany for substance-related prototype approvals for tank Containers in Germany. Compatibility evaluations of selected metallic materials and polymeric materials under the influence of approximately 7200 dangerous goods have been published in the BAM-List since 1989. The austenitic CrNi- and CrNiMo-steels - UNS S30403, UNS S31600, UNSS31603 and UNS S31635 - are the materials mostly used worldwide for transport tanks. The duplex Steel UNS S31803 has been put on the BAMList due to the great interest of tank producers and transport Companies. Using UNS S31803 instead of 316L, the weight of the tanks can be reduced, and the list of transportable goods can be extended. The objective of these investigations was to compare the corrosion resistance of duplex Steel UNS S31803 and austenitic Steel UNS S31603. Therefore, test specimens of both steels were exposed to selected corrosive substances, such as formic acid, acetic acid, phosphoric acid, sulfuric acid, nitrating acid, monochloroacetic acid and trichloroacetone at 55 °C (30 °C, 70 °C). The test results have shown that the duplex Steel UNSS31803 is a good alternative to austenitic CrNiMo-steel UNS S31603 for tanks carrying corrosive dangerous goods.
Biodiesel (FAME) from rapeseed is an environmentally friendly alternative to common fossil fuels. It is also suitable to serve as blending component to fuels like heating oil. If the fuel composition is changed, materials compatibility must be guaranteed. Adding polar biodiesel to nonpolar heating oil, changes the blend’s solvency and might cause swelling, extraction and solvation of polymers.
The objective of this research was to investigate the compatibility of polymeric materials, which are commonly used for components in middle distillate facilities, along with blends of heating oil and 20 % biodiesel (B20). For this propose, ACM, HNBR, FKM, PE, PA 6, POM, PUR and PVC were exposed to heating oil and B20 for 42 and 84 days at 40 °C. In addition, the polymers HNBR, FKM, PA, POM and PVC were also exposed at 70 °C. Furthermore, the resistance of polymers in eight-year aged B10 at 40 °C was evaluated. Ageing of biodiesel increases acidity which might propagate polymer corrosion.
The materials were evaluated as resistant, if the loss in tensile properties (tensile strength and elongation at break) and Shore hardness remained under 15 % compared to the initial unexposed material values. For investigations under compressed conditions, the compression set was determined for specimens of ACM, FKM and HNBR after exposure in heating oil B0 and B20 for 3,7,14, 28, 56 and 90 days at 40 °C according to ISO 815-1.
It was found that the resistance in B20 at 40 °C was given for all tested polymers except PUR. In the 8 years aged B10, PUR and POM were not compatible and ACM just conditionally compatible. At 70 °C, FKM and PVC were resistant in B20, whereas HNBR and PA 6 were not compatible. Swelling occurred for the elastomers ACM, HNBR and PUR.
Biodiesel (FAME) from rapeseed is an environmentally friendly alternative to common fossil fuels. It is also suitable to serve as blending component to fuels like heating oil. If the fuel composition is changed, materials compatibility must be guaranteed. Adding polar biodiesel to nonpolar heating oil, changes the blend’s solvency and might cause swelling, extraction and solvation of polymers. The objective of this research was to investigate the compatibility of polymeric materials, which are commonly used for components in middle distillate facilities, along with blends of heating oil and 20 % biodiesel (B20). For this propose, ACM, HNBR, FKM, PE, PA 6, POM, PUR and PVC were exposed to heating oil and B20 for 42 and 84 days at 40 °C. In addition, the polymers HNBR, FKM, PA, POM and PVC were also exposed at 70 °C. Furthermore, the resistance of polymers in eight-year aged B10 at 40 °C was evaluated. Ageing of biodiesel increases acidity which might propagate polymer corrosion. The materials were evaluated as resistant, if the loss in tensile properties (tensile strength and elongation at break) and Shore hardness remained under 15 % compared to the initial unexposed material values. For investigations under compressed conditions, the compression set was determined for specimens of ACM, FKM and HNBR after exposure in heating oil B0 and B20 for 3,7,14, 28, 56 and 90 days at 40 °C according to ISO 815-1. It was found that the resistance in B20 at 40 °C was given for all tested polymers except PUR. In the 8 years aged B10, PUR and POM were not compatible and ACM just conditionally compatible. At 70 °C, FKM and PVC were resistant in B20, whereas HNBR and PA 6 were not compatible. Swelling occurred for the elastomers ACM, HNBR and PUR.
CO2 quality specifications are not only a matter of CO2 purity (i.e. CO2 content).
The “rest” also matters, in particular contents of reactive impurities affecting material corrosion (and rock alteration).
Also chemical reactions in CO2 stream needs to be considered, in particular when combining CO2 streams of different compositions.
Finally, it can be summarized that the second edition of this popular textbook provides a comprehensive overview on the practical basics and applications of conducting polymers. It fulfills its intension of assisting various researchers from diverse fields to become familiar with fundamentals and applications of conducting polymers.
In this also completely rewritten and reorganized second part of the two‐volume set 45 international experts comprise the current knowledge of conjugated polymers. In addition to part one on properties, processing characterization and morphology, 16 chapters cover perspectives, theory and new materials.
Finally, it can be concluded that this 4th edition of this handbook fulfills, like the first part, its intention, to be the definitive resource on the topic of conducting polymers. This is assured by the updated and added contributions of all authors, which consider the significant developments both in fundamental understanding, progress and applications since publication of the previous edition. So, it can be recommended to everyone, who wants to get a comprehensive overview on conjugated polymers, not just to researchers, advanced students, and industry professionals working in materials science and engineering.
Interfacial properties related to wettability and corrosion in CO2 transport pipelines are experimentally determined by the sessile and the pendant drop methods. The contact angle of a water drop in a compressed CO2 atmosphere is analyzed on an X70 pipeline carbon steel and compared to that on a martensitic steel S41500 to elucidate the effect of corrosion process on active wetting behaviour. The measurements are performed with liquid CO2 at 278 K and pressures ranging from 5 to 20 MPa. The results show that the contact angle (CA) increases with pressure from 132 ° to 143 ° for S41500 and from 117 ° to 137 ° for X70 and decreases with drop age by 20 ° to 24 ° regardless of the pressure and of the fact that corrosion only occurs on X70, which is confirmed by scanning electron microscopy, element mapping and energy dispersive x-ray spectrometry (EDS) analysis. At higher pressure, the contact angles on both materials converge. Further, related properties like density and interfacial tension were determined. CO2 - saturated water has a higher density than pure water: At 5 MPa saturated water reaches a density of 1017 kg⋅m^(-3) and at 20 MPa 1026 kg⋅m^(-3) compared to pure water with a density of 1002 kg⋅m^(-3) and 1009 kg⋅m^(-3), respectively. In this pressure range the IFT drops from 33 mN⋅m^(-1)at 5 MPa to 23 mN⋅m^(-1) at 20 MPa.
This contribution provides current findings regarding materials susceptibility for carbon capture, utilization and storage (CCUS) applications. Basing on results gathered in 2 German long-term projects (COORAL and CLUSTER) suitable materials are introduced as well as dominating impurities of the CO2-stream and corrosion mechanisms. Investigations cover the whole CCUS process chain and provide material recommendations for certain parts.
This contribution provides current findings regarding materials susceptibility for carbon capture, utilization and storage (CCUS) applications. Basing on results gathered in 2 German long-term projects (COORAL and CLUSTER) suitable materials are introduced as well as dominating impurities of the CO2-stream and corrosion mechanisms. Investigations cover the whole CCUS process chain and provide material recommendations for certain parts.
The geological storage of carbon dioxide (Carbon Capture and Storage, CCS) in depleted gas reservoirs or in saline aquifers is a widely discussed issue. Carbon dioxide may induce corrosion on the piping steels during compression, transportation and injection. Therefore,
selection of appropriate piping steels is a key factor in order to increase the safety and reliability of the CCS technology, and to keep the processes cost-effective.
The here described subproject of the COORAL project (German acronym for “C02 purity for capture and storage”) deals with the levels of impurities in the C02 stream that will be acceptable when using specific steels. Material exposure to carbon dioxide (C02) containing
specific amounts of water vapor, oxygen (02) sulfur dioxide (S02), nitrogen dioxide (N02), carbon monoxide (CO) can be a challenge to steels. Within this subproject 13 different Steels are tested for suitability as materials used for compression, transportation and injection Units within the CCS chain.
Within the last years the use of geothermal energy as feasible energy source has risen and is going to replace fossil fuel supply more and more. Nevertheless, Service conditions in geothermal facilities are due to the Chemical composition of hydrothermal fluids and temperatures, in many cases, extreme in terms of corrosion. Since the construction of geothermal power plants shall be economical with maximum life Service, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable Operation ofthose facilities.
The materials selection depends on the location of a power plant respectively on the Chemical composition of the produced aquifer fluid. The duplex Steel is often used as allround solution not only for the construction of geothermal power plants, because of its combination of good mechanical and corrosion properties and its lower costs compared to other highly alloyed materials. But there are limits for the use of the duplex-steel 1.4462 regarding its corrosion behavior, with which this contribution deals.
The limitations of suitability of duplex steel 1.4462 in the geothermal fluids of Molasse Basin and Upper Rhine Graben obtained by means of electrochemical measurements and exposure tests are presented below. While 1.4462 in the artificial Molasse Basin Fluid shows an excellent corrosion resistance against pitting and uniform corrosion it presents low corrosion resistance in the artificial Upper Rhine Graben Fluid due to the difference in salinity. Besides it shows a limited corrosion resistance concerning crevice corrosion.
Since geothermal wells are a feasible energy source to replace fossil fuel supply, many technologies have been developed to take advantage of geothermal energy. Nevertheless, service conditions in geothermal facilities are due to the chemical composition of hydrothermal fluids and temperatures, in many cases, extreme in terms of corrosion. Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of the facilities.
This contribution deals with the evaluation of the corrosion behavior of duplex steel S31803 (318LN, X2CrNiMoN22-5-3, 1.4462) conducted by electrochemical measurements and exposure tests in artificial geothermal waters simulating the conditions in different locations with geothermal potential in Germany.
The duplex steel S31803 shows limited suitability for applications in artificial geothermal waters due to its susceptibility to pitting and crevice corrosion.
For low saline geothermal waters it can be considered suitable at moderate temperatures. Slight crevice corrosion susceptibility needs to be considered.
Results are being incorporated into a materials catalogue for geothermal applications which shall provide basic information for designers and users of geothermal facilities.
Since geothermal wells are a feasible energy source to replace fossil fuel supply, many technologies have been developed to take advantage of geothermal energy. Nevertheless, service conditions in geothermal facilities are due to the chemical composition of hydrothermal fluids and temperatures, in many cases, extreme in terms of corrosion. Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of the facilities.
This contribution deals with the evaluation of the corrosion behavior of duplex steel S31803 (318LN, X2CrNiMoN22-5-3, 1.4462) conducted by electrochemical measurements and exposure tests in artificial geothermal waters simulating the conditions in different locations with geothermal potential in Germany.
The duplex steel S31803 shows limited suitability for applications in artificial geothermal waters due to its susceptibility to pitting and crevice corrosion.
For low saline geothermal waters it can be considered suitable at moderate temperatures. Slight crevice corrosion susceptibility needs to be considered.
Results are being incorporated into a materials catalogue for geothermal applications which shall provide basic information for designers and users of geothermal facilities.
Corrosion behavior of high-alloyed materials in an artificial geothermal fluid at service conditions
(2010)
C02-corrosion on piping steels might cause problems during injection of flue gases for their storage in deep geological aquifer fluids. Therefore, the selection of appropriate piping steels is a key factor to increase safety and reliability of the Carbon Capture and Storage (CCS) technology, and to keep the process cost-efficient.
Within the project COORAL (German acronym for “C02 purity for capture and storage”) corrosion studies on injection piping steels exposed to C02 and artificial brine with high Chloride concentration have been carried out. Corrosion of the injection pipe in C02-rich aquifer fluid may occur within the aquifer brine or when at injection interruptions the aquifer fluid may flow back into the injection pipe. Because of high salinity of aquifer brine and C02-corrosion an appropriate material ranking of injection piping steels should be made.
Corrosion resistance of steels 1.4034, 1.4021, 1.4542, 1.4162 and 1.4562 was investigated in a corrosive environment using electrochemical and metallographic techniques. Electrochemical experiments in order to investigate the surface corrosion kinetics and polarization measurements in order to investigate localized corrosion phenomena have been carried out. Critical pitting potentials and repassivation potentials were determined by polarization curves of investigated materials and compared with measured corrosion potentials. Measured values were used in order to determine the suitability and performance of tested steels in C02-injection conditions.
The process chain for Carbon Capture and Sequestration (CCS) includes tubing for injection of CO2 into saline aquifers. The compressed CO2 is likely to contain specific impurities; small concentrations of SO2 and NO2 in combination with oxygen and humidity are most harmful. In addition, CO2 saturated brine is supposed to rise in the well when the injection process is interrupted. The material selection has to ensure that neither CO2 nor brine or a combination of both will leak out of the inner tubing. In this comprehensive paper the investigated materials range from low-alloy steels and 13% Cr steels up to high-alloy materials. Electrochemical tests as well as long term exposure tests were performed in CO2, in brine and combination of both; pressure was up to 100 bar, temperature up to 60 °C. Whereas the CO2 stream itself can be handled using low alloy steels, combinations of CO2 and brine require more resistant materials to control the strong tendency to pitting corrosion. The corrosion behavior of heat-treated steels depends on factors such as microstructure and carbon content. For different sections of the injection tube, appropriate materials should be used to guarantee safety and consider cost effectiveness.
The corrosion behaviour of martensitic stainless injection-pipeline steel X46Cr13 exposed to CO2 saturated artificial saline brine with high chloride concentration similar to onshore CCS-site at Ketzin, Germany has been investigated by means of electrochemical technique and microscopic observations at short exposure times (up to 24?h) and by mass loss and metallographic observations at exposure times up to 17520?h. Pitting corrosion kinetics has been characterised and the predictions about the corrosion mechanism are made.
Geothermal energy is an interesting alternative to polluting fossil energy sources. Therefore, in Belgium, two wells have been drilled for a deep geothermal power plant. However, the environment to which the installations are exposed is challenging. The geothermal brine has 165 g/l total dissolved solids (of which 90% are sodium and chlorine) and the production temperature can be up to 130 °C. To assess their suitability to be used in a geothermal power plant, the corrosivity of the artificial brine to three common construction materials was investigated with exposure and electrochemical tests. The metals under consideration are a low-alloyed carbon steel (S235JR), an austenitic stainless steel (UNS S31603) and a duplex stainless steel (UNS S31803). The carbon steel, that was found to corrode uniformly, could be considered as a constructional material if a sufficient wall thickness is chosen. The austenitic stainless steel and the duplex stainless steel demonstrate very low uniform
corrosion rates. They are however susceptible to pitting and crevice corrosion. To guarantee safe operation of the geothermal power plant, the susceptibility of the alloys to stress corrosion cracking should be tested and in situ experiments should be performed.
A global transition towards more sustainable, affordable and reliable energy systems is being stimulated by the Paris Agreement and the United Nation's 2030 Agenda for Sustainable Development. This poses a challenge for the corrosion industry, as building climate‐resilient energy systems and infrastructures brings with it a long‐term direction, so as a result the long‐term behaviour of structural materials (mainly metals and alloys) becomes a major prospect. With this in mind “Corrosion Challenges Towards a Sustainable Society” presents a series of cases showing the importance of corrosion protection of metals and alloys in the development of energy production to further understand the science of corrosion, and bring the need for research and the consequences of corrosion into public and political focus. This includes emphasis on the limitation of greenhouse gas emissions, on the lifetime of infrastructures, implants, cultural heritage artefacts, and a variety of other topics.
Finally it can be summarized that this book fulfills its intention of providing theoretical background and examples for practical applications of coatings used for corrosion protection.
It can be recommended to those being interested in coatings, serving as an overview on aspects which needs to be considered when working with such systems.
Commercially available carbon steels are suitable for compression and pipelines as long as moisture content and impurities are limited. (water 50 to 100 ppmv, SO2 and NO2 ca. 100 ppmv) Corrosion rates increase with increasing water content. (0.2 – 20 mm/a) Condensation of acids and therefore droplet formation is always possible, even at low water contents. A low SO2 content within the CO2-stream might be more important than a low water content. Cr13-steels showed a general susceptibility to shallow pitting and pitting. So, they seem to be not suitable for CCUS applications. Low alloyed steels showed better corrosion behavior (predictable uniform corrosion). For direct contact with saline aquifer fluids only high alloyed steels shall be used.
This study focuses on the corrosion mechanism of carbon steel exposed to an artificial geothermal brine influenced by carbon dioxide (CO2) gas. The tested brine simulates a geothermal source in Sibayak, Indonesia, containing 1500 mg/L of Cl-, 20 mg/L of SO4 2-, and 15 mg/L of HCO3-with pH 4. To reveal the temperature effect on the corrosion behavior of carbon steel, exposure and electrochemical tests were carried out at 70 °C and 150 °C. Surface analysis of corroded specimens showed localized corrosion at both temperatures, despite the formation of corrosion products on the surface. After 7 days at 150 °C, SEM images showed the formation of an adherent, dense, and crystalline FeCO3 layer. Whereas at 70 °C, the corrosion products consisted of chukanovite (Fe2(OH)2CO3) and siderite (FeCO3), which are less dense and less protective than that at 150 °C.
Control experiments under Ar-environment were used to investigate the corrosive effect of CO2. Free corrosion potential (Ecorr) and electrochemical impedance spectroscopy (EIS) confirm that at both temperatures, the corrosive effect of CO2 was more significant compared to that measured in the Ar-containing solution. In terms of temperature effect, carbon steel remained active at 70 °C, while at 150 °C, it became passive due to the FeCO3 formation. These results suggest that carbon steel is more susceptible to corrosion at the near ground surface of a geothermal well, whereas at a deeper well with a higher temperature, there is a possible risk of scaling (FeCO3 layer). A longer exposure test at 150 °C with a stagnant solution for 28 days, however, showed the unstable FeCO3 layer and therefore a deeper localized corrosion compared to that of seven-day exposed specimens.
Condensates from the gas stream in simulated CO2 transport pipelines have been identified during the experiments in the laboratory. Because of their acidic origin the corrosion resistance of pipeline steels used for CCS (carbon capture and storage) technology might be limited. Over the last years it has become clear that the amount of water and acid building constituents in the CO2 stream has to be controlled very well. In this work, condensates formed in experiments using gaseous CO2 containing high amounts of water, NO2 and SO2 were analyzed, replicated, and used for extensive electrochemical experiments. These highly acidic condensates were enriched with CO2 and then applied to characteristic steels planned to use in the CCS transport chain. Even high alloy steels are susceptible to localized corrosion under these conditions. The results implicate that condensation of aggressive acid droplets has to be avoided or the locations where condensation takes place have to be controlled extensively.
The composites combining aluminum and silica nanoparticles with the addition of tetramethylammonium hydroxide (Al-SiO2(T)) and butanol (Al-SiO2(B)) as mixing media have been successfully fabricated. Corrosion behavior of Al-SiO2 composites before and after exposure in 1M NaCl solution was examined using potentiodynamic polarization (Tafel curve analysis). The study was also equipped with scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD) investigations. Before exposure, Al-SiO2(T) exhibited the best corrosion resistance. Performance improvement was indicated by Al-SiO2(B) up to 10 times better than Al-SiO2(T) after exposure. The increased SiO2 content did not significantly enhance the corrosion resistance of the composites. The Al-SiO2 composites with 5% SiO2 content showed very high corrosion resistance (as the optimum composition). Furthermore, pitting corrosion was observed in the Al-SiO2 composites, indicated by the formation of corrosion products at grain boundaries. The product was affected by the presence of SiO2 in the Al matrix and the NaCl environment at 90 °C (approach to synthetic geothermal media: Na+, Cl, H+, OH-). Our study revealed the presence of γ-Al2O3, γ-Al(OH)3, and Al(OH)2Cl as the dominant corrosion products.
Corrosion resistance of high-alloyed and alternative materials in an artificial geothermal water
(2014)
Many technologies have been developed to take advantage of geothermal energy, which became a feasible energy source to replace fossil fuel supply. Nevertheless, service conditions in geothermal facilities are due to the chemical composition of hydrothermal fluids and involved high temperatures, in many cases, extreme in terms of corrosion. Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of the facilities.
This contribution deals with the evaluation of the corrosion behavior of two high-alloyed metallic materials and α-Al2O3 in an artificial geothermal fluid simulating the conditions in the Northern German Basin, a location with high geothermal potential. The suitability of the super austenitic stainless steel UNS N08031 and the nickel base alloy UNS N06059 in this geothermal fluid obtained by electrochemical measurements and exposure tests is addressed. As an alternative to the suitable but costly UNS N06059 that showed excellent corrosion resistance against pitting corrosion, ceramic made of α-Al2O3 represents an interesting possibility for selected components to be used in the construction of geothermal facilities