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In order to provide basic information on corrosion resistance to the designers and users of geothermal plants different metallic materials 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. By electrochemical and long-term exposure tests at 100 °C and 150 °C the suitability of low alloyed steel UNS G41300, stainless steels UNS S31603 UNS S31803, UNS S32760, super austenitic steel UNS N08031 and nickel based alloy UNS N06059 was investigated in these geothermal fluids, using critical potentials and corrosion rates. In high-saline environments the crevice corrosion turned out to be the determining mechanism. The nickel based alloy shows excellent corrosion resistance against pitting corrosion. Excluding its high cost, it is very good 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. Therefore they are not suitable for highly saline brines. The super austenite UNS N08031 showed a temperature depending behavior. In non-saline environments the low-alloyed steel UNS G41300 (beside of the higher alloyed materials) could be employed as a constructional material for the geothermal power plant, as long as a sufficient wall thickness of the material is considered.
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 low alloyed steel UNS G41300, stainless steels UNS S31603 UNS S31803, UNS S32760 and super austenitic steel UNS N08031 in these geothermal fluids, investigated by electrochemical measurements and exposure tests, is limited. The nickel based alloy UNS N06059 shows 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 UNS G41300 could be employed as a constructional material for the geothermal power plant in non-saline environments, as long as the wall thickness of the material vs. corrosion rate is taken into account.
Geothermal systems in Indonesia - Influence on the corrosion resistance of stainless steel materials
(2014)
The growth in a global demand for energy, as well as the awareness of a significant climate change, have evolved a very strong incentive for utilizing and expanding the use of clean and renewable energy resources. Geothermal energy is considered as one of a few alternatives ideal for replacing conventional sources due to its consistency and reliability, and is receiving ever more attention. However, geothermal Systems are found to be the most aggressive natural environments in terms of corrosion. High temperature and pressure conditions, as well as the existence of almost an entire periodic System of elements in form of corrosive salts, present a major threat to the integrity of the construction material. Therefore, in order to achieve a safer and continuous energy production, and increase the competitiveness of geothermal energy on the world scene, a comprehensive assessment of the materials suitability is of high importance for operators and vendors. Finally, thäs would lead to an inoreased lifespan of the power plant, as well as its economic profit, due to the reduced maintenance costs.