In-situ Surface Observation of Zn and Zn-5%Al Alloy in Aqueous Solution by Polarization Modified Infrared Reflection Absorption Spectrometry

The metal/liquid interface of Zn and Zn-5% Al alloy in aqueous solution has been investigated by means of polarization modified infrared reflection absorption spectrometry (PM-IR-RAS) as an in-situ surface observation technique. The experimental set up consists of an in-situ cell in which the aqueous solution is introduced and an optical system for PM-IR-RAS, which is designed so that spectra can be obtained during exposure of the metal sample to aqueous solution in an in-situ cell. It was found that surface OH at/or near Zn and Zn-5% Al alloy in aqueous solution was presented more than Pt. After immersion in water, a precipitated layer of Zn(OH)2 was detected on the surface of Zn-5% Al alloy coating, but it was not detected on Zn. Aluminum in Zn coating would prevent Zn(OH)2 from changing into ZnO.