AUTHOR=Zhu Wen , Chen Furui , Luo Youbin , Su Zhijun , Li Wenfang , Yi Aihua , Liao Zhongmiao , Li Kang , Chen Ken , Hu Yiwen , Xu Yashu , Guo Sinan 

TITLE=Vanadium and Tannic Acid-Based Composite Conversion Coating for 6063 Aluminum Alloy

JOURNAL=Frontiers in Materials

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2021.802468

DOI=10.3389/fmats.2021.802468

ISSN=2296-8016

ABSTRACT=<p>In this study, a vanadium (V) and tannic acid-based composite conversion coating (VTACC) was prepared on 6063 aluminum alloy (AA6063) to increase its corrosion resistance. The surface morphology and compositions of the VTACCs were characterized using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the coatings was investigated by linear polarization and electrochemical impedance spectra (EIS). The self-healing ability of the coating was detected by SEM, EDS, and scanning vibrating electrode technique (SVET) measurements. The coating mainly consisted of metal oxides, including Al<sub>2</sub>O<sub>3</sub>, VO<sub>2</sub>, V<sub>2</sub>O<sub>3</sub>, and V<sub>2</sub>O<sub>5</sub>, and metal organic complexes (Al and V-complexes). The electrochemical measurement results indicated that the best corrosion resistance of VTACC was acquired when the treatment time was 12 min. Furthermore, because a new coating with vanadium rich oxide was developed on the scratch area, artificial scratch VTACC surfaces were repaired after several days of immersion in 3.5-wt% NaCl solution.</p>