| Title | Challenges for Green Inhibitor Development for Geothermal Applications |
|---|---|
| Authors | Harry Tookey |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | Corrosion, Chemical Inhibitor, Corrosion Products, Salinity, Carbon Steel |
| Abstract | Carbon steel within geothermal systems can be impacted by corrosion due to carbon dioxide (CO2) dissolved in the fluid. Chemical inhibitors are typically used to mitigate the corrosion. However, many corrosion inhibitors are toxic and environmentally harmful. These factors mean a more environmentally friendly and sustainably sourced inhibitor to mitigate corrosion in geothermal energy systems is desired. As conditions can vary significantly in different geothermal sites, this presents challenges when evaluating the performance of new chemical inhibitors and understanding the corrosion rate and mechanisms of different systems. Therefore, the effect of high sodium chloride (NaCl) concentrations on the corrosion rate of carbon steel was studied to understand the corrosion mechanisms in simulated, high-salinity geothermal environments. Experiments were performed on X65 carbon steel coupons in aqueous CO2-saturated conditions at 2, 12 and 24 wt.% NaCl concentrations. All tests were at 80 °C, and pH of 6.2 and 6.8 were chosen. Under these conditions, iron carbonate (FeCO3) forms on the carbon steel coupons. The increase in NaCl concentration did not relate to an increase in the protective layer forming, with 12 wt.% having the most significant reduction in corrosion rate. The introduction of two different inhibitors showed that the chemistries can be impacted by NaCl concentration, with differing performances at the three concentrations. As the need for more sustainable and environmentally friendly chemical inhibitors becomes greater, one of the most widely researched areas is using Amino Acids as corrosion inhibitors. Due to the large number of Amino Acids, testing can be time-consuming. |