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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.
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.
The corrosion behavior of different high-alloyed metals including duplex and austenitic stainless steels as well as a nickel alloy have been evaluated in artificial geothermal fluids simulating the conditions in some locations with geothermal potential in Germany as well as two sites in Indonesia.
The suitability of carbon steel 25CrMo4, stainless steels X2CrNiMo17-12-2, X2CrNiMo-22-5, X2CrNiMoCuWN25-7-4 and super austenitic steel X1CrNiMoCu32-28-7 in these geothermal fluids obtained by electrochemical measurements and exposure tests is limited. The nickel alloy NiCr23Mo16Al shows an excellent corrosion resistance against pitting corrosion. Excluding its high cost, it is a very good alternative to be used in the construction of geothermal facilities having highly saline brines. Stainless and duplex steels exhibit a limited corrosion resistance concerning pitting and crevice corrosion.
Beside of the higher alloyed materials, also the low-alloyed steel 25CrMo4 could be employed as a constructional material for the geothermal power plant in stagnant highly acidic non saline environments, as long as the wall thickness of the material vs. corrosion rate is taken into account.
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. The corrosion behavior of different high-alloyed metals including Duplex and austenitic stainless steels as well as a nickel alloy have been evaluated in artificial geothermal fluids simulating the conditions in some locations with geothermal potential in Germany as well as two sites in Indonesia. The suitability of carbon steel 25CrMo4, stainless steels X2CrNiMo17-12-2, X2CrNiMo-22-5, X2CrNiMoCuWN25-7-4 and super austenitic steel X1CrNiMoCu32-28-7 in these geothermal fluids obtained by electrochemical measurements and exposure tests is limited. The nickel alloy NiCr23Mo16Al shows an excellent corrosion resistance against pitting corrosion. Excluding its high cost, it is a very good alternative to be used in the construction of geothermal facilities having highly saline brines. Stainless and Duplex steels exhibit a limited corrosion resistance concerning pitting and crevice corrosion. Beside of the higher alloyed materials, also the lowalloyed steel 25CrMo4 could be employed as a constructional material for the geothermal power plant in stagnant highly acidic non Saline environments, as long as the wall thickness of the material vs. corrosion rate is taken into account.
Corrosion Resistance of the Super-Austenitic Stainless Steel UNS S31266 for Geothermal Applications
(2017)
Super-austenitic stainless steels cover grades with high chromium (20 to 27 %), high nickel (18 to 31 %) and high molybdenum (4 to 6 %) contents. Within this family, the 6%Mo high nitrogen grade S31266 was developed to combine the beneficial influence of chromium, tungsten, molybdenum and nitrogen on its mechanical and corrosion properties. Due to 22 % nickel, 24 % chromium and 0.4 % nitrogen additions, this alloy exhibits a very stable microstructure, being less prone to intermetallic phase precipitation than the other highly alloyed super-austenitic stainless steels.
This paper deals with the corrosion resistance of S31266 in artificial geothermal water with moderate salinity and low pH. Long-term static exposures and electrochemical tests were conducted at various temperatures to evaluate the pitting, crevice and stress corrosion cracking resistance of this material.
The results show that S31266 is resistant up to 220 °C. As a consequence, it can be a good candidate material for geothermal applications involving a highly corrosive environment, especially salinity and low pH.
Corrosion Resistance of the Super-Austenitic Stainless Steel UNS S31266 for Geothermal Applications
(2017)
Super-austenitic stainless steels cover grades with high chromium (20 to 27 %), high nickel (18 to 31 %) and high molybdenum (4 to 6 %) contents. Within this family, the 6%Mo high nitrogen grade S31266 was developed to combine the beneficial influence of chromium, tungsten, molybdenum and nitrogen on its mechanical and corrosion properties. Due to 22 % nickel, 24 % chromium and 0.4 % nitrogen additions, this alloy exhibits a very stable microstructure, being less prone to intermetallic phase precipitation than the other highly alloyed super-austenitic stainless steels.
This paper deals with the corrosion resistance of S31266 in artificial geothermal water with moderate salinity and low pH. Long-term static exposures and electrochemical tests were conducted at various temperatures to evaluate the pitting, crevice and stress corrosion cracking resistance of this material.
The results show that S31266 is resistant up to 220 °C. As a consequence, it can be a good candidate material for geothermal applications involving a highly corrosive environment, especially salinity and low pH.
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.
By exposure and electrochemical tests in the laboratory the Cu-effect on corrosion behavior of carbon steel, high-alloyed steels and Ti-alloy can be assessed.
Critical materials specific properties were determined by static exposure and electrochemical tests in an artificial geothermal water with high salinity and low pH, containing Cu. Conclusions were drawn using characteristic potential values.
It could be shown that significant Cu-deposition and -precipitation only occurred in combination with carbon steel. High-alloyed materials (S31603, S31653, S31700, S31703, S31803 and N08904) prevent the disturbing Cu-agglomeration. Therefore, they are suitable to be chosen for future design of the piping system, either in massive or in cladded form, if formation of crevices with non-metallic materials can be excluded.
From the interactions and pitting corrosion point of view, R50400 seems to be most favorable.
Influence of Precipitating Brine Components on Materials Selection for Geothermal Applications
(2021)
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 in many cases extreme in terms of corrosion due to the chemical composition of hydrothermal fluids and temperatures. Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of the facilities. During operation of a geothermal research facility in Groß Schönebeck copper and lead effects have been found downhole. Occurring mechanisms and measures to prevent precipitation or scaling needed to be investigated as well as potential influences of such precipitates on corrosion resistance of metallic materials used for equipment.
This contribution deals with the evaluation of the corrosion behavior of carbon steel and corrosion resistant alloys in copper and/or lead containing artificial geothermal water, simulating the conditions in the Northern German Basin.
The behavior of these materials in an artificial geothermal water obtained by electrochemical measurements and exposure tests are presented. While carbon steel exhibits precipitation and deposition, higher alloyed material shows different response to such species and a higher resistance in saline geothermal water.
Basing on these results the suitability of the investigated corrosion resistant alloy is given for use in such conditions, whereas carbon steel creates difficulties due to its susceptibility to Cu- and Pb-precipitation.
Influence of Precipitating Brine Components on Materials Selection for Geothermal Applications
(2021)
By exposure and electrochemical tests in the laboratory the Cu- and Pb-effect on corrosion behavior and performance of carbon steel and a corrosion resistant alloy could be assessed. Critical material specific properties were determined by static exposure and electrochemical tests in artificial geothermal water with high salinity and low pH, containing Cu/Pb.
It could be shown that significant Cu- resp. Pb-deposition and precipitation only occurred in combination with carbon steel. Corrosion resistant alloys (e. g. Cr- and Ni-dominated stainless steels) prevent the disturbing Cu-agglomeration resp. Pb-deposition. Therefore, they are suitable to be chosen for future design of geothermal piping system, either in massive or in cladded form. Regarding corrosion, formation of crevices with non-metallic materials shall be avoided.
So, in addition to its already known limited corrosion resistance, carbon steel shall not be used when copper or lead species are content of the geothermal brine. Otherwise precipitation and/or deposition of metallic copper resp. lead must be expected, increasing the susceptibility of clogging the piping system.
From the interactions and pitting corrosion point of view, corrosion resistant alloys (preferably Ni-rich) seem to be most favorable when selecting materials for applications in such geothermal brines.