Date of Award

Fall 10-8-2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

School

Polymer Science and Engineering

Committee Chair

Dr. James Rawlins

Committee Chair School

Polymer Science and Engineering

Committee Member 2

Dr. Robson Storey

Committee Member 2 School

Polymer Science and Engineering

Committee Member 3

Dr. Jeffrey Wiggins

Committee Member 3 School

Polymer Science and Engineering

Committee Member 4

Dr. Derek Patton

Committee Member 4 School

Polymer Science and Engineering

Committee Member 5

Dr. Gopinath Subramanian

Committee Member 5 School

Polymer Science and Engineering

Abstract

This dissertation aimed at answering several fundamental questions, specifically: 1) What is the effect of scribing parameters on visual corrosion assessments? 2) What role do molecular weight, residual solvent, and polymer composition have on morphological changes in organic thin films? 3) What alternatives to visual assessments could be implemented to better understand and detect corrosion before macroscopic failure? This research definitively proved that scribes can vary in type and dimensions, and yet are still comparable if the scribe dimensions before exposure are known. Furthermore, it demonstrated that solvents common to a variety of coating industries could become trapped within the polymeric film. Whether trapped through chemical interactions or physical limitations due to vitrification of the film, these solvents ultimately affect the modulus, Tg, and adhesion in a dramatic, complex, but detectable manner. In addition, when water-miscible solvents are utilized, they are ultimately exchanged with water and result in voids during water uptake and solvent exchange. In clear films, these voids are largely detectable without the use of aided optics as the films whiten as a result of refractive index differences between the voids and the polymeric material. However, these same results were observed in commercial pigmented thermoplastic coatings through the use of electron microscopy. The impact of these voids formed through solvent selection has yet been in the corrosion literature, and this research affords a foundation from which new formulations can be created. Lastly, the use of fluorescein was validated quantitatively for the detection of cathodic delamination, correlated with scanning Kelvin probe. These cathodically delaminated areas were quantified through a shift to basic pH at the coating-metal interface. Additionally, a ratiometric technique using fluorescein and rhodamine B was established to determine the apparent pH at the substrate-coating interface without the need for additional experiments. The development of correlative techniques and manipulation of morphological features resulting from solvent cast polymeric thin film formulation and application conditions provided predictive results from which a specific threshold can be selectively shifted to facilitate inhibitor release rates, lower testing durations, and achieve higher throughput life-cycle assessments of coatings.

ORCID ID

0000-0002-3335-7968

Available for download on Friday, June 07, 2019

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