Evaluation of Suitability of Some High Alloyed Materials for Geothermal Applications

In the last years geothermal power has become a reliable and significant energy source. Because service conditions in geothermal facilities from deeply located aquifers are critical in terms of corrosion, a very important issue regards materials selection. Preliminary evaluation of the materials suitability represents therefore a valuable strategy to ensure a secure and reliable operation of the facilities. In geothermal applications, the use of high-alloyed materials likes stainless steels and nickel-based alloys has been considered as a good alternative. This paper presents recent experiences from laboratory test performed on the super duplex steel alloy F55 ( X2CrNiMoCuWN25-7-4), the alloy 31 (X1NiCrMoCu32-28-7) and the nickel-based alloy 59 (NiCr23Mo16Al) in an artificial geothermal fluid having the chemical composition of  the highly saline aquifer of “North German Basin”. Tests carried out in this artificial fluid including exposure tests and electrochemical investigations at 100°C and 150°C showed the limits of suitability concerning pitting and crevice corrosion of these materials for geothermal applications.