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Effect of Calcium Ions and CaCO3 Scale on the CO2 Corrosion Mechanism

Calcium ions are usually present at high concentrations in brines produced with oil and gas. Such brines are typically saturated with respect to CaCO3. Consequently precipitation of CaCO3 as scale on the internal wall of the pipeline can readily occur due to changes in operational and environmental parameters when produced fluids are transmitted from downhole to surface facilities. Despite its importance there is minimal research in the literature addressing the effect of calcium ions and specifically CaCO3 scale on the CO2 corrosion mechanism. Moreover the available literature on this topic is contradictory with undefined water chemistry and flow characteristics of the employed experimental setups. This highlights the need for further systematic experimental studies in this frequently ignored area of corrosion research. The main objectives of this work were to further broaden the mechanistic understanding of CO2 corrosion of mild steel (pH from 5.5 to 6.2 with [Ca2+] from 160 to 6000 ppm to simulate CaCO3 saturation) and evaluate the protectiveness of CaCO3 (without the interference of ferrous ions) against further corrosion; a novel experimental methodology was developed and utilized. The corrosion behavior was studied in situ by electrochemical methods including linear polarization resistance (LPR) electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) along with weight loss (WL) methods for a UNS G10180 with ferritic-pearlitic microstructure. Surface characterization of the scale and corrosion product was performed using scanning electron microscopy (SEM) energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques. Unprotective CaCO3 scale was observed to act as a mass transfer barrier that can promote surface conditions favoring FeCO3 precipitation. Contrary to previous reported research the presence of CaCO3 scale did not result in onset of localized corrosion at the conducted experimental conditions. 

Product Number: 51319-13000-SG
Author: Hamed Mansoori
Publication Date: 2019
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$20.00
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51313-02358-Effect of Calcium Ion on the Formation and Protectiveness of Iron Carbonate Layer in CO2 Corrosion

Product Number: 51313-02358-SG
ISBN: 02358 2013 CP
Author: Saba Navabzadeh Esmaeely
Publication Date: 2013
$20.00