In aqueous carbon dioxide (CO2) corrosion of carbon steels, the presence of calcium ions influences the kinetics of corrosion product formation and can affect both general and localized forms of attack. When conducting laboratory experiments, understanding the transient solution chemistry due to the corrosion process is critical when evaluating the effects of calcium on corrosion behavior. Autoclave experiments were conducted at 80°C and 5 barg with 3 brines containing 0, 1000 and 5000 mg/l of Ca2+. Iron flux into the brine was varied using high and low area to volume (A/V) ratios. Results from mass loss and electrochemical measurement techniques show that the presence of calcium reduces initial corrosion rates but slows down the formation of more protective corrosion product layers. A higher A/V ratio led to much faster corrosion product formation and altered the composition of the resulting corrosion products in the presence of calcium ions. The results demonstrate how conflicting views on the role of calcium can be observed depending on the A/V ratio and test duration.

Subject
Steel surfaces, Fluxes, Corrosion rate, Mass loss, Autoclaves, Calcium, Corrosion products, Corrosion scales, Scale formation, Brines, Carbon steel, Corrosion protection, Linear polarization resistance
Keywords:
CO2 Corrosion, carbon steel, calcium, CaCO3, FeCO3, electrochemistry, autoclaves, LPR
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2022
Association for Materials Protection and Performance (AMPP)
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