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51318-11192-Investigation of FeCO3 and FeS Precipitation Kinetics by EQCM

In the present study, the precipitation kinetics of iron carbonate (FeCO3) and iron sulfide (FeS) were studied over a range of temperatures to gain a better understanding of their effect on corrosion resistance.

Product Number: 51318-11192-SG
Author: Zheng Ma / Yang Yang / Bruce Brown / Srdjan Nesic / Marc Singer
Publication Date: 2018
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Corrosion product layers play a key role in the corrosion processes by precipitating on the steel surface and can lead either to enhanced corrosion protection or, in some cases, to severe pitting, depending on the conditions. The kinetics of precipitation of corrosion product layers has a direct impact on the layers properties and their level of protectiveness. In the present study, the precipitation kinetics of iron carbonate (FeCO3) and iron sulfide (FeS) were studied over a range of temperatures to gain a better understanding of their effect on corrosion resistance. An Electrochemical Quartz Crystal Microbalance (EQCM) was used to investigate the FeCO3 precipitation kinetics in an aqueous CO2 environment, as well as the FeS precipitation kinetics in an aqueous H2S environment. In addition, different substrates were used to isolate specific aspects of the precipitation mechanisms: a cathodically polarized gold-coated quartz crystal, a cathodically polarized iron-coated quartz crystal, and a freely corroding iron-coated quartz crystal were used for FeCO3 precipitation; the two latter ones were used for FeS precipitation. The measured precipitation rates in both environments were repeatable and consistent across different substrates and over the range of temperatures tested. The FeCO3 precipitation rates exhibited a relatively strong dependency on system temperature and bulk saturation level of FeCO3. However, FeS precipitation kinetics appeared only weakly sensitive to the change of temperature. In addition, it is also postulated that the FeS saturation level at the substrate surface (rather than in the bulk), should be taken into consideration when the bulk saturation level of FeS is relatively low. The theoretical kinetic constant and the activation energy for both FeCO3 and FeS (based on bulk) were derived from the obtained EQCM results and compared with literature values.

Keywords: EQCM, iron carbonate, iron sulfide, precipitation kinetics

Corrosion product layers play a key role in the corrosion processes by precipitating on the steel surface and can lead either to enhanced corrosion protection or, in some cases, to severe pitting, depending on the conditions. The kinetics of precipitation of corrosion product layers has a direct impact on the layers properties and their level of protectiveness. In the present study, the precipitation kinetics of iron carbonate (FeCO3) and iron sulfide (FeS) were studied over a range of temperatures to gain a better understanding of their effect on corrosion resistance. An Electrochemical Quartz Crystal Microbalance (EQCM) was used to investigate the FeCO3 precipitation kinetics in an aqueous CO2 environment, as well as the FeS precipitation kinetics in an aqueous H2S environment. In addition, different substrates were used to isolate specific aspects of the precipitation mechanisms: a cathodically polarized gold-coated quartz crystal, a cathodically polarized iron-coated quartz crystal, and a freely corroding iron-coated quartz crystal were used for FeCO3 precipitation; the two latter ones were used for FeS precipitation. The measured precipitation rates in both environments were repeatable and consistent across different substrates and over the range of temperatures tested. The FeCO3 precipitation rates exhibited a relatively strong dependency on system temperature and bulk saturation level of FeCO3. However, FeS precipitation kinetics appeared only weakly sensitive to the change of temperature. In addition, it is also postulated that the FeS saturation level at the substrate surface (rather than in the bulk), should be taken into consideration when the bulk saturation level of FeS is relatively low. The theoretical kinetic constant and the activation energy for both FeCO3 and FeS (based on bulk) were derived from the obtained EQCM results and compared with literature values.

Keywords: EQCM, iron carbonate, iron sulfide, precipitation kinetics

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06644 KINETICS OF IRON SULFIDE AND MIXED IRON SULFIDE/CARBONATE SCALE PRECIPITATION IN CO2/H2S CORROSION

Product Number: 51300-06644-SG
ISBN: 06644 2006 CP
Author: Wei Sun,Sankara Papavinasam, Srdjan Nesic
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