Applications and limitations of scanning kelvin probe force microscopy for the surface analysis of aluminum alloys

The surface properties of aluminum alloy 2024-T3 (AA2024-T3) sheet after several surface treatments were investigated using scanning Kelvin probe force microscopy (SKPFM) and scanning electron microscopy (SEM). Treatments included boiling water, sodium chloride solution, and a chromate-free deoxidizing solution. The ability of SKPFM to resolve contact potential differences on both polished and rolled AA2024-T3 surfaces has been evaluated. While sensible data could be obtained on rolled sheet surfaces, SKPFM on pitted surfaces proved to be problematic. The inability of the scanning tip to accurately trace the surface topography resulted in erroneously high contact potential differences. Polished AA2024-T3 was analyzed by SEM before and after oxide growth. Carbon deposits on polished AA2024-T3 occurring during SEM analysis were revealed as areas with contact potential contrast using SKPFM. The influence of oxide thickening on contact potential differences was explored for AA2024-T3 and pure copper foil. The applicability of SKPFM for studying intermetallic features on other aluminum and other common engineering alloys is discussed. (c) 2006 The Electrochemical Society.