The economic utilization of geothermal resources with temperatures less than 220oF for purposes other than electric power generation (direct utilization) requires creation of systems with long plant life and minimum operation and maintenance costs. Development of such systems requires careful corrosion engineering if the most cost effective material selections and design choices are to be made. This study guide presents guidelines for materials selection for low-temperature geothermal systems (120 - 200oF), as well as guidance in materials design of heat pump systems for very low temperature geothermal resources (less than 120oF)