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51313-02269-Material Evaluation for Application in Geothermal Systems in Indonesia

Product Number: 51313-02269-SG
ISBN: 02269 2013 CP
Author: Amela Keserovic
Publication Date: 2013
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Geothermal energy is considered one of a few alternatives ideal for replacing conventional polluting fossil fuels due to its cleanliness consistency reliability and the ability to provide baseload power. Despite the expensiveness of the project development long-term costs of running a geothermal power station are extremely low. One of the major impacts on overall expenses has the constructional material. Due to the highly concentrated solutions of corrosive salts at high temperatures and pressures present in geothermal systems a huge risk of equipment degradation and failure is present if inadequate and insufficient measures regarding the material selection are taken. This could not only lead to the curtailment in power plant energy production but also in the worst case to the complete plant shutdown. Therefore it is of crucial importance to choose suitable materials which would in the same time withstand such aggressive environments and still be cost-effective. That way a reliable and secure geothermal power plant operation would be achieved and its longer lifetime.
The purpose of this study was to investigate the occurrence of various types of corrosion (uniform pitting and crevice corrosion) on different steel grades (chromium steel 25CrMo4 stainless steel X2CrNiMo17-12-2 and highly alloyed stainless steel X1NiCrMoCu32-28-7) by means of electrochemical methods and exposure tests. The research was carried out in a synthetic geothermal fluid (1.5 g/L chlorides 0.02 g/L sulfates pH 4.00) at 100 °C and 175 °C simulating the conditions present at the geothermal site Sibayak (North Sumatra Indonesia).
The results show chromium steel 25CrMo4 does not have an acceptable corrosion resistance in the investigated conditions. Its free corrosion potential is in the range of critical values. Therefore active corrosion would be expected as it was proven by exposure tests. In contrast free corrosion potentials of higher alloyed materials are far away from the critical values and a good repassivation behavior can be observed as well. Hence no corrosion attack by the medium would be expected. Even in the case of system variations the material would repassivate when returning to normal conditions.
Although both higher alloyed investigated materials show excellent results in terms of corrosion resistance stainless steel X2CrNiMo17-12-2 should be used for such application preferably to highly alloyed stainless steel X1NiCrMoCu32-28-7 due to its lower cost.

Keywords: geothermal corrosion steel electrochemistry
 

Geothermal energy is considered one of a few alternatives ideal for replacing conventional polluting fossil fuels due to its cleanliness consistency reliability and the ability to provide baseload power. Despite the expensiveness of the project development long-term costs of running a geothermal power station are extremely low. One of the major impacts on overall expenses has the constructional material. Due to the highly concentrated solutions of corrosive salts at high temperatures and pressures present in geothermal systems a huge risk of equipment degradation and failure is present if inadequate and insufficient measures regarding the material selection are taken. This could not only lead to the curtailment in power plant energy production but also in the worst case to the complete plant shutdown. Therefore it is of crucial importance to choose suitable materials which would in the same time withstand such aggressive environments and still be cost-effective. That way a reliable and secure geothermal power plant operation would be achieved and its longer lifetime.
The purpose of this study was to investigate the occurrence of various types of corrosion (uniform pitting and crevice corrosion) on different steel grades (chromium steel 25CrMo4 stainless steel X2CrNiMo17-12-2 and highly alloyed stainless steel X1NiCrMoCu32-28-7) by means of electrochemical methods and exposure tests. The research was carried out in a synthetic geothermal fluid (1.5 g/L chlorides 0.02 g/L sulfates pH 4.00) at 100 °C and 175 °C simulating the conditions present at the geothermal site Sibayak (North Sumatra Indonesia).
The results show chromium steel 25CrMo4 does not have an acceptable corrosion resistance in the investigated conditions. Its free corrosion potential is in the range of critical values. Therefore active corrosion would be expected as it was proven by exposure tests. In contrast free corrosion potentials of higher alloyed materials are far away from the critical values and a good repassivation behavior can be observed as well. Hence no corrosion attack by the medium would be expected. Even in the case of system variations the material would repassivate when returning to normal conditions.
Although both higher alloyed investigated materials show excellent results in terms of corrosion resistance stainless steel X2CrNiMo17-12-2 should be used for such application preferably to highly alloyed stainless steel X1NiCrMoCu32-28-7 due to its lower cost.

Keywords: geothermal corrosion steel electrochemistry
 

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Product Number: 51313-02268-SG
ISBN: 02268 2013 CP
Author: Stein Olsen
Publication Date: 2013
$20.00