Corrosion testing of UNS S31603 in simulated HT geothermal environment at boiling, superheated and condensation conditions

Corrosion testing of austenitic stainless steel, UNS S31603 (AISI 316L), was conducted in flow-through reactors during early stages of lab setup development with the aim to obtain a superheated steam environment with H2S/CO2/HCl at 350°C and 10 bars. The test fluid; aqueous solution with the corrosive species was preheated, boiled and superheated in preheater before entering the reactors. But due to regular high-volume injection periods of the aqueous solution into the preheater and insufficient thermal insulation surrounding the test unit, a liquid droplet transportation into the reactors and condensation of the test fluid in the reactors was experienced. After the corrosion testing, the corrosion rate of the samples varied quite significantly, and different corrosion forms were observed. The corrosion rate was determined with weight loss analysis and the corrosion forms were analyzed with SEM, XEDS, XRD and light microscope. The aim of corrosion testing was to simulate high temperature geothermal environment i.e. IDDP-1 (Iceland Deep Drilling well #1) conditions where previous on-site corrosion testing of some alloys had been conducted. The experiment casts a light on different corrosion behavior of the UNS S31603 at boiling/superheated/condensation conditions which is to be expected during the heat-up and discharge period of deep drilled wells as well as working conditions (superheated).