Characterization of the surface properties of iron oxides

Abstract A series of iron oxides, α-Fe 2 O 3 and α-FeOOH, which have been identified as products formed during corrosion, have been characterized with respect to their surface properties and the effect of surface treatments by water adsorption isotherm measurements. The pretreatment conditions included high-temperature activation up to 400°C, hexamethyldisilazane (HMDS) treatment, and treatment with methanol. The results show that for both iron oxides dehydroxylation of the surface occurs partially at 400°C, followed by rehydroxylation after exposure to water vapor at room temperature. The HMDS treatment was found to effectively hydrophobe the surface to an extent which is limited by the bulky nature of this molecule, where the cross-sectional area of this molecule is estimated at 40 A 2 . Experimental conditions were found whereby a relatively small molecule, such as methanol, could interact chemically and quantitatively with surface hydroxyls to hydrophobe the surface more effectively. The stability of this type of treatment for extended periods of time is currently under further investigation.