De Motte, Rehan Anthony (2016) A Combined Experimental and Modelling Approach to Elucidate FeCO3 Scale Formation Kinetics. PhD thesis, University of Leeds.
Abstract
In CO2 corrosion, when the local concentrations of Fe2+ and CO32- ions exceed the solubility limit, precipitation of iron carbonate (FeCO3) can occur internally within pipework, forming a protective corrosion barrier at the steel-electrolyte interface. Accurately quantifying the rate of precipitation of this film is important within the oil and gas industry as it can be implemented into corrosion prediction tools to provide a more reliable estimate of anticipated corrosion rates.
Existing precipitation rate models are based on measurements conducted in a glass cell in static conditions where the kinetics of FeCO3 precipitation are accelerated by the addition of FeCl2.4H2O and correlated with bulk solution properties. They do not address the key aspects of FeCO3 formation in real corroding systems which relate to the local surface supersaturation produced as a result of the production of Fe2+ ions due to the corrosion process.
In the following thesis, a combined experimental and modelling approach is carried out to investigate the development in the morphology of the FeCO3 film under different environmental conditions and its consequent effect on the degradation rates of a pipeline. A thin channel flow cell is designed to extend the analysis to a fluid flow environment and a mechanistic model is developed to predict the nature of the near surface layer.
It is found from the experimental analysis that FeCO3 precipitation is a simultaneous nucleation and growth process and the characteristics of the surface film significantly changes under varying parameters. Results show that the existing precipitation models based on measuring the dissolved ferrous ions in the bulk solution overestimate the precipitation of iron carbonate by a large margin and the precipitation model developed through the direct weight change approach is limited to the experimental conditions in which it was carried out. The models are correlated with bulk solution properties and it has been clearly demonstrated within this work that the precipitation of FeCO3 is directly related to the conditions at the steel surface which can be very different from that in the bulk. A combined model and experimental analysis shows that a higher initial surface saturation ratio indicates a more protective film formation over time.
Metadata
Supervisors: | Neville, Anne N. and Barker, Richard B. |
---|---|
Keywords: | CO2 Corrosion, FeCO3 film formation, corrosion modelling, precipitation |
Awarding institution: | University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering (Leeds) > School of Mechanical Engineering (Leeds) > Institute of Engineering Thermofluids, Surfaces & Interfaces (iETSI) (Leeds) |
Identification Number/EthosID: | uk.bl.ethos.701730 |
Depositing User: | Mr. Rehan Anthony/ R.A. De Motte |
Date Deposited: | 23 Jan 2017 10:54 |
Last Modified: | 25 Jul 2018 09:53 |
Open Archives Initiative ID (OAI ID): | oai:etheses.whiterose.ac.uk:16062 |
Download
Final eThesis - complete (pdf)
Filename: A Combined Experimental and Modelling Approach to Elucidate FeCO3 Scale Formation Kinetics.pdf
Licence:
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License
Export
Statistics
You do not need to contact us to get a copy of this thesis. Please use the 'Download' link(s) above to get a copy.
You can contact us about this thesis. If you need to make a general enquiry, please see the Contact us page.