Cross-sectional characterization of the conversion layer formed on AA2024-T3 by a lithium-leaching coating

Journal article (2020)

Authors

A. Kosari (OLD) MSE-6
P. Visser Akzo Nobel
F.D. Tichelaar QN/Afdelingsbureau , Kavli institute of nanoscience Delft
S. Eswara Luxembourg Institute of Science and Technology
J. N. Audinot Luxembourg Institute of Science and Technology
T. Wirtz Luxembourg Institute of Science and Technology
H.W. Zandbergen Kavli institute of nanoscience Delft, QN/Zandbergen Lab
H.A. Terryn Vrije Universiteit Brussel, (OLD) MSE-6
J.M.C. Mol (OLD) MSE-6
Research Group
(OLD) MSE-6
Copyright: © 2020 A. Kosari, P. Visser, F.D. Tichelaar, S. Eswara, J. N. Audinot, T. Wirtz, H.W. Zandbergen, H.A. Terryn, J.M.C. Mol
DOI
help_outline
https://doi.org/10.1016/j.apsusc.2020.145665
AA2024-T3 Energy Filtered TEM High Resolution TEM Layered double hydroxide Leachable lithium carbonate SIMS
More Info
expand_more

Published Date

2020

Language

English

Research Group

(OLD) MSE-6

Abstract

This work focuses on the cross-sectional characterization of the protective conversion layer formed on AA2024-T3 by lithium-leaching from a polyurethane coating in a corrosive environment. The layer shows a multi-layered arrangement comprising nanoscopic local phases. Transmission electron microscopy (TEM) and complementary high-resolution secondary ion mass spectroscopy (SIMS) were employed to observe the cross-sections of the entire layer formed at different locations of a 1-mm-wide scribe, in terms of morphology, structure and chemical composition. The conversion layer was comprised of two ubiquitous sublayers; a thin dense layer (i.e. 150 nm) adjacent the alloy substrate and a porous layer. The former represents an amorphous lithium-containing pseudoboehmite phase, Li-pseudoboehmite, whereas the latter is composed of amorphous and crystalline products; an outer columnar layer merely seen on the peripheral region is also crystalline. Through a sandwich structure and the d(003) basal spacing, the crystalline phases were identified as Li-Al layered double hydroxide. Although lithium was found uniformly spread within different regions, the local phases with no/low concentration of lithium were revealed with energy filtered TEM and confirmed with SIMS analysis.