Characterisation of the surface chemistry of magnesium exposed to the ambient atmosphere

The changes in the surface chemistry of the oxidised surface of evaporated magnesium metal stored in the ambient atmosphere are studied with water contact angle (WCA) measurement, polarisation-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and X-ray photoelectron spectroscopy (XPS). Upon exposure to the ambient atmosphere, the surface picks up volatile organic compounds (VOC), which cause a significant increase in the WCA values. The PM-IRRAS and XPS analyses indicate that the adsorbates contain hydrocarbons, carboxylates and carbonate functionalities. After long ambient storage times, the composition of the carbon-containing functionalities on the surface changes significantly. This change could be caused by the build-up and/or surf ace-catalysed oxidation of adsorbed organic species. Thickening of the air-formed oxide/hydroxide layer was also noted, ascribed to the reaction of adsorbed atmospheric moisture with the magnesium surface. Copyright (C) 2006 John Wiley & Sons, Ltd.