| Summary: | <p>Among the existing corrosion control methods, surfactant inhibitors have widely been used for corrosion inhibition of pipelines in water-oil-steel pipe (WOS) environments. This dissertation includes a systemic review of the causes of pipeline corrosion in WOS environments containing carbon dioxide (CO2), general corrosion control using surfactant inhibitors and associated concerns, and commonly used classes of surfactants and their properties, various processes and phenomena that affect overall surfactant performance. This dissertation also provides a review of experimental evaluation techniques and various developed models (semi-empirical model, mechanistic model, and multiphysics model) in evaluation of surfactant inhibition efficiency. An integrated corrosion inhibition (ICI) model is proposed, developed, and validated based on the current understanding of the inhibition of CO2 corrosion in WOS environments using surfactants.
The developed ICI model for the modeling and prediction of corrosion inhibition efficiency of mixed surfactant inhibitors is a multiphysics model, based on the fundamentals from many areas of corrosion science, electrochemistry, metallurgical engineering, and chemical and analytical engineering, etc., and the integration of several submodels, including a water-oil surfactant distribution submodel, the aqueous cmc prediction submodel, and the modified Langmuir adsorption (MLA)/ modified quantitative structure activity relation (MQSAR) submodel. Software is developed based on the ICI model and the use of computational and programming resources.
The phenomena and processes integrated into the ICI model include surfactant partitioning between oil and water, micellization and precipitation, adsorption/desorption at surfaces and interfaces, surfactant-solvent interactions, surfactant-counterion pairing, lateral interactions between surfactant molecules, and fluid flow. These phenomena are incorporated into three main processes and associated modeling: partitioning between oil and water, micellization/precipitation, and effective adsorption on metal substrate and water/oil interface.
The framework of multiphysics ICI model is intended to serve as a basic framework in the understanding of mixed surfactant inhibitor performance with a focus on the application in salt-containing WOS environments. Beyond this, other potential applications may be extended to the design of surfactants, selection of optimal surfactants for specific applications, experimental validation of developed models, simulation of conceivable processes and phenomena, and the integration into more comprehensive lifetime prediction models in which all the surfactant efficiency-affecting factors may be evaluated.
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