The precipitation kinetics of FeS were studied at varied system temperatures using an Electrochemical Quartz Crystal Microbalance (EQCM). Two different substrates were used for FeS precipitation studies: a cathodically polarized iron-coated quartz crystal, and a freely corroding iron-coated quartz crystal. Precipitation rates were repeatable and consistent when compared at the same temperature. Overall observations show that the precipitation rates of FeS were not very sensitive to the change of temperature. Analysis of the experimental data has also shown that the FeS saturation level on the substrate surface (SFeS,surface) should be taken into consideration when the bulk saturation level of FeS (SFeS,bulk) was relatively low, as the surface pH could be up to three units higher than the solution pH due to the cathodic polarization. The theoretical kinetic constant and the activation energy for FeS (valid only if SFeS,bulk > 1) were determined from the obtained EQCM results based on three possible FeS formation pathways.

Subject
Steel surfaces, Mackinawite, Precipitation (solids), Ion speciation, Substrates, Corrosion rate, Iron sulfides, Saturation, Quartz, Bulk solution, Substrate surfaces, Corrosion products, Constants
Keywords:
EQCM, iron carbonate, iron sulfide, precipitation kinetics
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2019
Association for Materials Protection and Performance (AMPP)
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