Scanning Kelvin Probe Study of (Oxyhydr)oxide Surface of Aluminum Alloy

In this paper, the work function, referenced as electrode potential vs SHE, of modified (oxyhydr)oxide surfaces of AA1050 was studied upon exposure to different relative humidity (40% and 90%) and aging (40 and 240 min) by utilizing scanning Kelvin probe (SKP). Besides reference samples, different pretreatments (acid, alkaline, and immersion in boiling water) were applied in order to create variations in the surface properties (i.e., hydroxyl content, oxide thickness, surface morphology). The observed trend in the potential was correlated to the hydroxyl fraction and the oxide thickness of the modified surfaces, determined by X-ray photoelectron spectroscopy and visible spectroscopic ellipsometry , respectively. Fourier transform infrared spectroscopy was also used to investigate the chemical composition of the modified surfaces. It is presented how the surface potential of aluminum (oxyhydr)oxide is influenced by the oxide properties, such as hydroxyl fraction and thickness. This characterization work on bare (oxyhydr)oxide aluminum surfaces is a preliminary study and opens a way to understand the contribution of oxide properties to the interfacial bonding in the presence of organic coating.