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Plasma polymerized coatings for improved corrosion resistance

Zhou, Yang
http://orcid.org/0000-0002-4276-6253
http://rave.ohiolink.edu/etdc/view?acc_num=akron1536785690423517

Abstract Details

2018, Doctor of Philosophy, University of Akron, Polymer Science.
Tens of billions of dollars are spent on corrosion problems every year in the US by the Department of Defense alone. Polymer coating systems are widely used for protecting the metal by preventing water transport through the coating and contact with the metal. Due to the environmental hazards associated with hexavalent chromium and volatile organic contents from traditional polymer coating systems, there is an urgent need to develop new types of coatings. These concerns have drawn attention to ecologically friendly coatings deposited with vapor deposition techniques like plasma enhanced chemical vapor deposition (PECVD). In this work, we not only have developed plasma polymerized (pp) coatings for improved corrosion resistance, but also have characterized their structures and properties with various techniques. Firstly, we started with plasma polymerized coatings from well-established vacuum based PECVD to understand their water resistance and corrosion resistance. An Al panel coated with plasma polymerized maleic anhydride (pp-MA) corroded after one day in salt spray, while a similarly thin (~30 nm) plasma polymerized hexamethyldisiloxane (pp-HMDSO) coating protected an Al panel for a period on the order of one month. The behavior seen with macroscopic tests was consistent with nanoscale characterization with Neutron Reflectivity and Sum Frequency Generation Spectroscopy that showed slow water penetration through a pp-HMDSO coating and water accumulation at the pp-MA/substrate interface. In addition, off specular X-ray measurement showed that the interfacial water disrupted the conformality of the pp-MA coating with the substrate. Secondly, we used plasma polymerized coatings as primer to improve the corrosion resistance of a whole coating system. Both electrochemical impedance spectroscopy (EIS) measurements and salt spray tests showed that using a thin pp-HMDSO coating as a primer under a polyurethane (PU) topcoat can increase the corrosion resistance by a factor of 10 times over that for a PU topcoat directly on an Al panel. The poorly adhesion to the topcoat with hydrophobic pp-HMDSO can be improved with gradient coatings using surface modification of the pp-HMDSO coating. The coatings with plasma polymerized primers showed better corrosion resistance than those of PU on Al and PU on chromate treated Al after 1-month, 3-month and 6-month field tests in a harsh seashore environment in Hawaii. Thirdly, we modified surface fluctuations of polymer melt films by modifying the substrate surface with PECVD. The surface fluctuations of polystyrene thin film with thickness around 3 Rg on pp-MA modified silicon substrate showed less confinement than did similarly thick films on bare silicon. There was no confinement for either case when film thickness was larger than 4 Rg. The difference in confinement was related to the different strongly adsorbed layers on the different substrates. The surface of a polystyrene thin film with thickness around 4 Rg on a pp-HMDSO modified silicon substrate showed faster fluctuations and cannot be described with the HCT theory. This could due to slip at the interface between PS and pp-HMDSO. Finally, we developed plasma polymerized organic coatings deposited in air using atmospheric pressure PECVD (APPECVD). A coating from the same precursor, HMDSO, deposited at atmosphere with APPECVD was hydrophilic and inorganic in character. Using the low oxygen content monomer tetramethylsilane or hexamethyldisilazane, we successfully developed hydrophobic coatings with higher relative carbon contents.
Mark Foster, Dr. (Advisor)
Ali Dhinojwala, Dr. (Advisor)
Mesfin Tsige, Dr. (Committee Chair)
Mark Soucek, Dr. (Committee Member)
Qixin Zhou, Dr. (Committee Member)
Polymers
plasma polymerized coating; corrosion; interface

Recommended Citations

Citations

  • Zhou, Y. (2018). Plasma polymerized coatings for improved corrosion resistance [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1536785690423517

    APA Style (7th edition)

  • Zhou, Yang. Plasma polymerized coatings for improved corrosion resistance. 2018. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1536785690423517.

    MLA Style (8th edition)

  • Zhou, Yang. "Plasma polymerized coatings for improved corrosion resistance." Doctoral dissertation, University of Akron, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1536785690423517

    Chicago Manual of Style (17th edition)

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This open access ETD is published by University of Akron and OhioLINK.