Advanced iron boride coatings to enhance corrosion resistance of steels in geothermal power generation

Iron boride coatings obtained by the CVD-based thermal diffusion process are proposed and evaluated for the first time for high-temperature corrosion and scaling conditions in geothermal power generation. The testing results in different corrosion environments are presented. The influence of structure and surface composition on the materials’ performance is demonstrated. The dual-layer boride-based coatings successfully withstand the actions of high temperature/high pressure water and steam with a presence of H2S, CO + CO2, chlorides and hydrocarbons in simulating conditions and strong acidic environments. They demonstrated minimal scaling and corrosion when the materials were immersed into the modelling mixes of chloride salt solutions with SiO2 or SiO2+Fe2O3 at elevated temperatures and into the brine solution at boiling. These advanced ceramic coatings and technology should promote significant extension of the steels’ service life in harsh geothermal-related corrosion environments.