Interaction of aliphatic acids and alcohols with aluminum surfaces

The present work examines the interaction of propanoic acid and 1-propanol, 1-butanol, 1-ethanol, and 1-hexanol with clean, oxidized, and anodized aluminum to identify the nature of the chemical bond on these surfaces. The investigations were carried out by x-ray photoelectron spectroscopy, at temperatures ranging from ∼20 to 500 °C. Initially at room temperature, chemisorbed acid molecules break up on clean Al, leading to attachment of aliphatic chain fragments to the surface via carbon atoms. As adsorption continues, acid molecules react with Al via the functional group to oxidize the surface. In contrast, aliphatic alcohols chemisorb on clean Al via the functional group alone. At elevated temperatures, the acid and alcohols dissociate on the clean surface along similar reaction paths. On oxidized and anodized surfaces, the acid and alcohols chemisorb via the functional group and desorb at elevated temperatures without molecular dissociation.