Abstract
The general and localized corrosion behaviour of X65 carbon steel and 5Cr low alloy steel were evaluated in a water-saturated supercritical CO2 environment in the presence of varying concentrations of O2. Experiments were performed at a temperature of 35°C and a pressure of 80bar to simulate the conditions encountered during CO2 transport and injection. Results indicated that increasing O2 concentration from 0 to 1000ppm caused a progressive reduction in the general corrosion rate, but served to increase the extent of localized corrosion observed on both materials. Pitting (or localized attack) rates for X65 ranged between 0.9 and 1.7mm/year, while for 5Cr rose from 0.3 to 1.4mm/year as O2 concentration was increased from 0 to 1000ppm. General corrosion rates were over an order of magnitude lower than the pitting rates measured. Increasing O2 content in the presence of X65 and 5Cr suppressed the growth of iron carbonate (FeCO3) on the steel surface and resulted in the formation of a corrosion product consisting mainly of iron oxide (Fe2O3). 5Cr was shown to offer more resistance to pitting corrosion in comparison to X65 steel over the conditions tested. At concentrations of O2 above 500ppm 5Cr produced general corrosion rates less than 0.04mm/year, which were half that recorded for X65. The improved corrosion resistance of 5Cr was believed to be at least partially attributed to the formation of a Cr-rich film on the steel surface which was shown using X-ray photoelectron spectroscopy to contain chromium oxide (Cr2O3) and chromium hydroxide (Cr(OH)3). A final series of tests conducted with the addition of 1000ppm O2 in under-saturated conditions (water content below solubility limit) revealed that no corrosion was observed when the water content was below 1200ppm for both materials.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.