Corrosion testing of materials in simulated superheated geothermal environment

Corrosion Behaviour of Titanium Alloy and Carbon Steel in a High-Temperature, Single and Mixed-Phase, Simulated Geothermal Environment Containing H2S, CO2 and HCl

“…The loss of material and the lack of corrosion film on the surface in the first few centimetres of sample 1 indicated that the acidic aqueous solution at high temperature caused the removal of the corrosion products at a rapid rate. The results also indicate that, further into the first reactor, the fluid became less corrosive and the corrosion behaviour trended towards a more localized corrosion attack, as observed in previous study by Thorhallsson et al, for materials tested in superheated conditions [15]. The corrosion behaviour observed for carbon-steel sample 5 in the second reactor resembled the corrosion behaviour observed for sample 1 after the first few centimetres.…”

“…The samples in between had, to a large extent, surface texture similar to the surface texture characterized by the presence of magnetite (see Figure 5 and Table 6). This had been observed in other corrosion tests performed in the same testing equipment (but with different setup) in a superheated environment done by Thorhallsson et al [15]. A broad range of corrosion forms was observed on the carbon-steel sample in the first few centimetres of sample 1: some locations had negligible oxide film observed on the surface; other locations had a dense oxide film present.…”

“…In a further attempt to homogenize the testing conditions, three flow-through reactors were connected in series where the first reactor was applied as a preheater. Several corrosion trials were conducted in this new setup, but results still indicated inhomogeneous conditions in the testing volume [24]. This was concluded from different corrosion behaviours in the samples in different locations in the testing volume.…”

“…The corrosive geothermal fluid consists mainly of H 2 O as steam with other corrosive species such as H 2 S and CO 2 (aqueous, gas or mixed-phase state) depending on the chemical composition of the fluid, the pressure and the temperature. The chemical composition and the phase state of the corrosive geothermal fluid affect the corrosion rate and behaviour of the material exposed to the corrosive geothermal fluid [15][16][17][18]. The phase state of the corrosive fluid affects its ionic activity, which strongly depends on the density of the fluid at high-temperature or in aqueous solutions [19,20].…”

“…This was concluded from different corrosion behaviours in the samples in different locations in the testing volume. Thorhallsson et al reported that further adjustments and modifications eventually led to homogeneous corrosion behaviour in the second and third reactor since the first reactor was only used as a preheater [15].…”