Corrosion and Material Selection for Geothermal Systems

Abstract

As geothermal energy is being developed and taking more importance, certain problems have occurred regarding the corrosion and the usage of the materials that are influence the effectiveness and the quality of the service. The knowledge of the characteristics of the geothermal fluid partly leading to the breakdown of the equipment used for processes due to corrosion, is very important in the equipment selection. Dissolved CO2, H2S, NH3 and chloride ions, may lead to the metallic materials being corroded and becoming unusable. The chemical composition, temperature, and velocity of fluid vary depending on the geothermal resource, the design of the power system, and the point of the production cycle. Both the operating experiences gained during usage and laboratory studies performed with real geothermal fluids form the basis for the selection of materials for this area. In this paper, the reasons for the corrosion types that are seen in geothermal systems are discussed, and the evaluation of the behavior of the materials according to the environmental conditions where the metallic and nonmetallic materials are found. Precautions have to be taken in order to utilize materials like steel, stainless steel in geothermal industry. Titanium, Inconel, and Hastolloy C-276 Ni-Cr-Mo alloys could be preferable for high temperature geothermal use. Concrete-polymer compounds, cement and fiber reinforced plastics and other non-metals are more useful because of their high corrosion resistance and reasonable cost especially for the geothermal heating using low-enthalpy fields.