The role of acetic acid in FeCO₃ scale deposition on CO₂ corrosion of API X65 carbon steel under high temperatures

Abstract

The combined effects of high temperatures and different acetic acid (HAc) concentrations on corrosion and deposition of FeCO 3 scales on API X65 carbon steel in CO 2 -saturated brines were investigated. Conditions with the absence and presence of 100 and 600 ppm of HAc were evaluated under high pressure at 90°C and 120°C. Electrochemical impedance spectroscopy, linear polarisation resistance, weight loss and characterisations through scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction were conducted. Conditions with the absence of acid presented a huge deposition of sweet corrosion products and low corrosion rates. The addition of 100 ppm of acid at 90°C did not increase significantly corrosion rates; however, it retarded the precipitation of FeCO 3 . Higher temperatures favoured iron carbonate nucleation even in the presence of HAc. The highest corrosion rates were observed for the environment with 600 ppm of HAc at 120°C.