| Title | Corrosion of Type 430 Stainless Steel at 250 ℃ in Acidic Fluids |
|---|---|
| Authors | Natsuki Hirabayashi |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | Corrosion, Acidic geothermal fluids, High chloride ions, Type 430 stainless steel, Processing strain |
| Abstract | Acidic geothermal fluids containing large amounts of chloride ions are an underutilized resource because of the occurrence of corrosion and scale deposition. To utilize this, data must be collected to predict corrosion of casing and aboveground piping. We implemented corrosion tests of stainless steel in acidic fluids in subcritical regions. Corrosion tests for type 430 stainless steel were conducted in acidic fluid with high chloride ions at 250 ℃. The stainless steel is a general-purpose stainless steel and can be used to reduce costs. In addition, we investigated the difference in corrosion behavior of the stainless steel with and without strain from the rolling process. Those were prepared without strain by solution treatment. The corrosion test was conducted for 3 days in an acidic fluid (pH = 3.5) with high chloride ions (NaCl = 30,000 ppm) produced by heating and pressurizing the fluid to 250 ℃ and 30 MPa. The test solution was continuously pumped into the vessel containing the specimens at a constant flow rate. Surface microstructures were analyzed using optical microscopy, SEM/EDS, and XRD. The experimental results indicated that specimens without strain exhibited less corrosion than those with it. The corrosion rate was approximately 0.5 mm/year for specimens with strain and about 0.3 mm/year for those without it. Pitting corrosion was observed in the specimens with strain. The specimens without the strain may prove advantageous in some applications. |