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Corrosion Resistance of the Super-Austenitic Stainless Steel UNS S31266 for Geothermal Applications

Update on recent experiences from laboratory tests performed at service conditions for geothermal applications.  Incorporated in a catalogue of suitable materials for applications geothermal power plants. Users shall be enabled to have a basis for designing such facilities.

Product Number: 51317--8825-SG
ISBN: 8825 2017 CP
Author: Ralph Baessler
Publication Date: 2017
Industry: Energy Generation
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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 UNS 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 less prone to intermetallic phase precipitation than the other highly alloyed super-austenitic stainless steels.  This paper will deal with the corrosion resistance of UNS S31266 in artificial geothermal water with high 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 this grade is resistant up to 220°C. As a consequence it can be a good candidate material for geothermal applications involving a highly corrosive environment.

Keywords: S31266, crevice corrosion, super-austenitic stainless steel, geothermal energy,

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 UNS 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 less prone to intermetallic phase precipitation than the other highly alloyed super-austenitic stainless steels.  This paper will deal with the corrosion resistance of UNS S31266 in artificial geothermal water with high 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 this grade is resistant up to 220°C. As a consequence it can be a good candidate material for geothermal applications involving a highly corrosive environment.

Keywords: S31266, crevice corrosion, super-austenitic stainless steel, geothermal energy,

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09377 Evaluation of Corrosion Resistance for Materials in Geothermal Applications

Product Number: 51300-09377-SG
ISBN: 09377 2009 CP
Author: Markus Finke, Ralph Babler, Ali Saadat, Rolf Kirchheiner and Andreas Burkert
Publication Date: 2009
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