CO2 tribocorrosion of CVD W/WC coatings and performance against internally epoxy coated pipes: A benchmark against HVOF WC-Cr3C2-NiCr and electroless Ni-P coatings

Abstract

CO₂ anoxic environments are often found in the energy sector in applications comprising oil and gas, geothermal energy or carbon capture and utilization, among others. These environments are highly corrosive, resulting in material degradation and ultimately component failure. A widely used option for mitigating degradation in CO₂ corrosive environments relies on the use of corrosion resistant coatings. However, these coatings are often exposed simultaneously to wear in many applications such as in sucker rods for the oil and gas industry, resulting in tribocorrsion. The separate corrosion or wear behavior of many industrial relevant corrosion resistant coatings has been previously widely reported in many works. However, knowledge about their tribocorrosion behavior is scarce and limited to atmospheric conditions, being the knowledge on their CO₂ tribocorrosion behavior inexistent. The present work shows under well-controlled electrochemical conditions that the specific wear rate of chemical vapor deposited W/WC and thermal spray WC-Cr₃C₂-NiCr coatings is up to three orders of magnitude lower when compared to electroless Ni-P coatings under point contact conditions and one order of magnitude lower under line contact conditions, despite all coatings offering a good corrosion resistance under high pressure CO₂. The experiments performed under line contact conditions also reveal that the former coatings are also suitable for protecting components sliding against abrasive epoxy coatings. These results highlight the importance of simultaneously evaluating the wear performance of coatings in reactive environments in order to select coatings suitable for protecting sliding components in CO₂ corrosive environments.