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Title:Scalable corrosion resistant coatings for thermal applications
Author(s):Khodakarami, Siavash
Advisor(s):Miljkovic, Nenad
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Abstract:Corrosion of metallic substrates is a problem for a variety of applications. Corrosion can be mitigated with the use of an electrically insulating coating protecting the substrate. Thick millimetric coatings, such as paints, are generally more corrosion resistant when compared to nanoscale coatings. However, for thermal systems, thick coatings are undesirable due to the resulting decrease in overall heat transfer stemming from the added coating thermal resistance. Hence, the development of ultra-thin (< 10 μm) coatings is of great interest. Ultra-thin inorganic silicon dioxide (SiO2) coatings applied by sol-gel chemistries or chemical vapor deposition, as well as organic coatings such as Parylene C have great anti-corrosion performance due to their high dielectric breakdown and low moisture permeability. However, their application to arbitrarily shaped metals is difficult or expensive. Here, we develop a sol-gel solution capable of facile and controllable dip coating on arbitrary metals, resulting in a very smooth (< 5 nm roughness), thin (~ 3 μm), and conformal coating of dense SiO2. To benchmark our material, we compared the corrosion performance with in-house synthesized superhydrophobic aluminum and copper samples, Parylene C coated substrates, and smooth hydrophobic surfaces functionalized with a hydrophobic self-assembled monolayer. To comparison with state-of-the-art commercial coatings, copper substrates were coated with an organo-ceramic SiO2 layer created by an elevated temperature and atmospheric pressure metal organic chemical vapor deposition process (AP MO-CVD). To characterize corrosion performance, we electrochemically investigated the corrosion resistance of all samples through potentiodynamic polarization studies and electrochemical impedance spectroscopy. To benchmark the coating durability as well as to demonstrate scalability, we tested internally coated copper tubes in a custom-built corrosion flow loop to simulate realistic working conditions with shear and particulate saltwater flow. The sol-gel and Parylene C coatings demonstrated a 95% decrease in corrosion rate during electrochemical tests. Copper tube weight loss was reduced by 75% for the sol-gel SiO2-coated tubes when seawater was used as the corrosive fluid in the test loop. This work not only demonstrates scalable coating methodologies for applying ultra-thin anti-corrosion coatings, but it also develops a mechanistic understanding of corrosion mechanisms on a variety of functional surfaces and substrates.
Issue Date:2021-04-30
Rights Information:Copyright 2021 Siavash Khodakarami
Date Available in IDEALS:2021-09-17
Date Deposited:2021-05

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