Ionic liquid enhanced electrochemical characterization of transport phenomena

Brian Hinderliter, Kerry Allahar, Gordon Bierwagen, Dennis Tallman, Stuart Croll

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Metallic additives provide sacrificial protection and complement the barrier protection afforded by heterogeneous organic coatings to metallic substrates. The transport of materials, water in particular, into, out, and within a coating has a significant impact on the effectiveness of the coating as a barrier and as a medium for sacrificial protection additives. Recent papers from our group have introduced the methodology whereby room temperature ionic liquids (RTIL5) in conjunction with capacitance monitoring via electrochemical impedance spectroscopy (ElS) can be used to determine the diffusion coefficient of water out of a non-pigmented, additive free coating.4 This methodology is extended in this effort to a Zn-rich epoxy that is used as a primer for Army vehicles. The RTILs are electrically conductive consisting of large molecules, can be used to investigate the electrochemical properties of coatings in a non-aqueous medium, and for hydrophilic RTILs, can be used to extract water from a wet coating. An experiment was conducted to simulate the alternate wetting and drying of the Zn-rich epoxy. The capacitance evolution associated with the exposure of the coating on a steel substrate to cycles comprising of 0.05 M NaCI wetting and RTIL drying is presented in Figure 1. The capacitance data obtained from these experiments were analyzed using models to separate the Fickian transport of water into and out the coating from the percolation of water through pores. ElS experiments were also conducted on the Zn-rich epoxy under constant immersion in 0.05 M NaCI and RTIL. The wet-dry cycling procedure resulted in the leaching of zinc containing species from the coating. The experimental results were analyzed to determine the dielectric response, void fraction changes, and dissolution rate of the zinc containing species associated with the coating.

Original languageEnglish (US)
Title of host publicationMaterials Research Society Symposium Proceedings - Transport Behavior in Heterogeneous Polymeric Materials and Composites
Pages22-31
Number of pages10
Volume1006
StatePublished - Dec 1 2007
EventTransport Behavior in Heterogeneous Polymeric Materials and Composites - 2007 MRS Spring Meeting - San Francisco, CA, United States
Duration: Apr 9 2007Apr 13 2007

Other

OtherTransport Behavior in Heterogeneous Polymeric Materials and Composites - 2007 MRS Spring Meeting
CountryUnited States
CitySan Francisco, CA
Period4/9/074/13/07

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