Self‐assembling behavior of TDPA molecules on inhomogeneous surface of 2024 aluminum alloy

The self-assembling behavior of 1-tetradecylphosphonic acid (TDPA) molecules on the surfaces of 2024 aluminum alloys was studied with an emphasis on the different micro-structural regions of the alloy surface, specially the alloy matrix and the two main types of intermetallic particles, as well as how the adsorption was effected by changes in water content of the self-assembly solution. Surface characterization was undertaken with contact angle measurement, scanning electron microscopy and Auger electron spectroscopy (AES). The packing density of TDPA film on the alloy surface increased with the increasing water content of the self-assembly solution. It seemed that the micro-distribution of TDPA molecules was related to copper amount and the region with a higher surface copper concentration had a lower packing density of TDPA. Some pits were formed in the acidic self-assembly solutions and the exposed surfaces of the pits can quickly adsorb TDPA molecules with compactness comparative to the matrix surface. Different adsorption models of TDPA corresponding to different water content of the self-assembly solution were suggested based on the analysis of AES depth sputtering data. Copyright © 2013 John Wiley & Sons, Ltd.