Interaction of a model epoxy resin compound, diethanolamine, with aluminium surfaces studied by static SIMS and XPS

The interaction of diethanolamine, a model epoxy resin compound, with aluminium surfaces is characterised using static secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS). Diethanolamine does not adsorb on gamma-alumina but does adsorb on phosphoric acid anodised aluminium, suggesting that the adsorption site is a Bronsted acid. A static SIMS spectrum is obtained consistent with a protonated species and the XPS N 1s signal shows two states for the adsorbate. Diethanolamine on an ion-bombarded aluminium surface does not show the characteristic SIMS spectrum observed with the anodised substrate. It is postulated that the hydroxy groups of the diethanolamine form a dialkoxide covalently bound to the ion-bombarded aluminium. The corresponding XPS N Is signal showed a single binding energy in the range of Lewis site interactions on alumina. The interaction of all three functionalities of the diethanolamine with the anodised aluminium surface results in stronger adsorption than for a similar difunctional compound, (methylamino)ethanol, indicating that both hydroxy groups are involved in hydrogen bonding to surface acid sites.