Suitability of UNS S31603 steel for geothermal brines in volcanic areas – Influence of different physicochemical conditions on its corrosion behavior

• Alloy exhibited resistance to pitting corrosion at temperatures up to 175 °C and pressures up to 900 kPa.
• Chloride concentration up to 1500 mg/L causes no pitting corrosion.
• Passive layer formation retarded at pH 2.
• Severe crevice corrosion at the metal-polymer occluded site.
• No cracks detected during 6 months exposure at 175 °C.

Geothermal sources are found to be the most aggressive natural environments for construction materials in terms of corrosion. This study was focused on investigating the suitability of stainless steel UNS S31603 in volcanic areas of geothermal sites Sibayak and Lahendong (Indonesia). Influence of different factors (temperatures up to 175 °C, chloride content up to 1500 mg/L and pH down to 2) was assessed to determine a “safe operating window” of a power plant and assure the system integrity. Investigations were performed by means of electrochemical methods and long-term exposure tests.