Considerations in the Testing and Selection of Materials for Corrosive Geothermal Environments

Abstract

Selection of cost effective materials of construction for geothermal applications requires that designers and operators recognize and understand the mechanisms by which candidate materials can degrade in the various geothermal fluids. Once the applicable degradation mechanisms are identified, the designer or operator can address: 1. The rate of degradation, which influences the expected time to failure or required frequency of repair, and thereby the lifecycle cost of candidate materials 2. The relative consequences of different failure mechanisms, 3. The influence of various manufacturing and fabrication practices on corrosion resistance, and 4. The ability of common inspection practices to detect the degradation so that it can be mitigated before failure occurs. This paper describes the process of selecting appropriate materials of construction through a sequence of steps that includes definition of the service environment, including likely upset conditions, preliminary materials selection, testing of candidate materials, evaluation of the test results, and in-service monitoring. Examples of common oversights and omissions in the material selection process are included.