- Author
- Nguyen, T. | Bentz, D. P. | Byrd, W. E.
- Title
- Study of Water at the Organic Coating/Substrate Interface.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Journal
- Journal of Coatings Technology, Vol. 66, No. 834, 39-50, July 1994
- Keywords
- water | substrates | coatings | ft-ir | formulations | quantitative analyses | thickness
- Abstract
- Quantitative information on the water layer at the coating/substrate interface is crucial for understanding and preventing the failure of organic coating systems. A method, based on a two-layered model derived rigorously from internal reflection theory, was developed for determining the amount and thickness of water at the organic coating/substrate interface. The method gives new insight into the processes by which water degrades the coating/substrate bonds. The method requires application of a transparent or opaque organic coating of sufficient thickness on an internal reflection element (IRE), which is used as the substrate. A water chamber is attached to the coated specimen. After adding water to the chamber, FTIR-MIR (Fourier transform infrared-multiple internal reflection) spectra are taken automatically at specified time intervals without disturbing the specimens or the instrument. Water uptake in the coating and FTIR-MIR spectra of water on the coating-free substrate are also used for the analysis. Results for a clear epoxy coating on a Ge substrate and a pigmented alkyd on an Si0₂-Si substrate are presented to demonstrate the method. In addition to measuring water at the coating/substrate interface, the method provides a means for studying the transport of water through a coating adhered to a substrate. Information obtained by this method is valuable for interpreting corrosion, blistering, and delamination of organic coating systems and for developing models for use in predicting the service lives of protective coatings.