A spectroscopic technique for in situ measurement of water at the coating/metal interface

Abstract

A technique was developed based on Fourier transform infrared spectroscopy in the multiple internal reflection mode (FTIR-MIR) for measuring in situ water at the coating/metal interface. The technique requires a direct application of a transparent or opaque polymer coating of any thickness to a Ge internal reflection element (IRE). A water chamber was attached to the polymer-coated IRE and water was introduced through the chamber inlet. FTIR-MIR spectra were taken automatically at specified time intervals without realignment or readjustment of the ATR accessory and without disturbing the specimens or the conditions of the experiment. The intensities of the water bands increased and those of the coating bands decreased initially and then leveled off as the exposure times increased. Calculations are presented to demonstrate that the technique can provide information on water at the coating/metal interface. The method may also provide a convenient means for measuring the diffusion of water in polymer coatings on metals.