Mechanism of LDH Direct Growth on Aluminum Alloy Surface: A Kinetic and Morphological Approach

abstract

The growth of ZnAl layered double hydroxide (LDH) on the AA2024 surface was monitored using synchrotron high-resolution X-ray diffraction. Data were analyzed using the Avrami-Erofe'ev kinetic model. Accordingly, the LDH film growth is governed by a two-dimensional (2D) diffusion-controlled reaction with a zero nucleation rate. Additional methods, including ex situ atomic force microscopy/scanning Kelvin probe force microscopy (AFM/SKPFM) supported by in situ open-circuit potential (OCP) measurements together with scanning electron microscopy (SEM) and transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM/EDX) analysis, provided further insight into the different stages of the mechanism of LDH growth. Prior to the conversion coating formation, an intermediate layer is formed as a basis for the establishment of the LDH flakes. Moreover, a Cu-rich layer was revealed, which could contribute to the acceleration of LDH growth. The formed LDH layer does not show any cracks at the interface but presents minor irregularities in the structure, which could favor adhesion to subsequent organic coatings. The findings presented in this work provide an important insight to the corrosion performance of the LDH conversion coatings and the pathway to adopt for further optimization.

keywords

LAYERED DOUBLE HYDROXIDES; CHROMATE CONVERSION COATINGS; CORROSION PROTECTION; COPPER DISSOLUTION; ALKALINE STABILITY; AQUEOUS-SOLUTIONS; 2024-AL ALLOY; PHASE-CHANGE; AA2024-T3; BEHAVIOR

subject category

Chemistry, Physical; Nanoscience & Nanotechnology; Materials Science, Multidisciplinary

authors

Bouali, AC; Iuzviuk, MH; Serdechnova, M; Yasakau, KA; Drozdenko, D; Lutz, A; Fekete, K; Dovzhenko, G; Wieland, DCF; Terryn, H; Ferreira, MGS; Zobkalo, IA; Zheludkevich, ML

Groups

G3 - Electrochemical Materials, Interfaces and Coatings

Projects

Projeto de Investigação Exploratória: Kyril Yasakao (IF/01284/2015)

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

MULTI-functional metallic SURFaces via active Layered Double Hydroxide treatments (MULTISURF)

Development and design of novel multiFUNctional PEO COATings (FUNCOAT)

acknowledgements

The authors acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at PETRA III under the proposal number I-20170366. The authors thank Dr. Sergey Volkov for his assistance in using the diffractometer in a P08 high-resolution diffraction beamline. The authors are also grateful to Dr. Petr Harcuba and Dr. Peter Minarik for their help with TEM lamella preparation and Dr. Miroslav Cieslar for his assistance during TEM operation. They thank Gert Wiese for his help with obtaining the SEM micrographs. A.C.B. and M.H.I. are grateful for the financial support of the German-Russian Interdisciplinary Science Center (G-RISC) in form of a travel grant (T-2018b-1 and T-2018a-3 respectively) that enabled them to perform a scientific exchange and complete this work. A.C.B. additionally thanks the EFC Young Scientist for awarding the EUROCORR Young Scientist Grant 2017, financially supporting her research stay among the SURF group at Vrije Universiteit Brussel and accomplishing a part of the current study. M.S. and M.L.Z. are also thankful to I2B fond for financial support of this work in frame of MUFfin project as well as the ACTICOAT project in frame of Era.Net RUS Plus Call 2017 (Project 477). K.A.Y. acknowledges researcher grant (IF/01284/2015). A part of this work was conducted within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the Portuguese Foundation for Science and Technology/MCTES. D.D. is grateful for the financial support of the Nanomaterials Centre for Advanced Applications (NANOCENT), grant number CZ.02.1.01/0.0/0.0/15_003/0000485 financed by ERDF. A.L. gratefully acknowledges the funding of VLAIO for the RECYCAL 2 project with the number HBC.2017.0300. Moreover, this work was the result of the participation of several other projects, namely, the European project MULTISURF and FUNCOAT in frame of the H2020-MSCA-RISE, grant agreement nos. 645676 and 823942, respectively.