Corrosion testing in superheated geothermal steam in Iceland

• Corrosion rates were extremely low (<0.1 mm/year) for all tested materials.
• Low corrosion rates explained by severe scaling and the high superheat in the steam.
• Despite low corrosion rates corrosion damages were evident in all materials tested.
• First SCC testing in superheated geothermal steam.
• Stress corrosion cracks were detected in UNS S31603, UNS S30403 and UNS S31803.

Corrosion testing was conducted in a superheated geothermal steam from the IDDP-1 well in Iceland at 360 °C for 113 days. Severe silica scaling occurred in the test. The average corrosion rate was extremely low; less than 0.1 mm/year for all the metals tested which can be explained by the combined protective effect of the silica and the high superheat in the steam preventing any condensation. Despite the low average corrosion rate, the microstructural analysis show that even the most corrosion resistant materials tested, such as UNS N06625 and titanium UNS R52400 show localized corrosion damage after the test. Only the low alloy stainless steels UNS S30403, UNS 31603 and UNS 31803 showed evidence of Stress Corrosion Cracking.