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Effects of Mn 2+ on the chrome‐free colored Ti/Zr‐based conversion coating on 6063 aluminum alloy
Author(s) -
Yi Aihua,
Li WenFang,
Du Jun,
Mu SongLin
Publication year - 2015
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.5788
Subject(s) - conversion coating , coating , materials science , nucleation , corrosion , x ray photoelectron spectroscopy , alloy , microstructure , crystal (programming language) , chemical engineering , layer (electronics) , raman spectroscopy , aluminium , metallurgy , chemistry , composite material , organic chemistry , optics , physics , computer science , engineering , programming language
The conversion coating with golden color and improved corrosion resistance had been prepared by adding Mn 2+ in the Ti/Zr conversion coating solution. Comparing with that of conversion coating without Mn 2+ , the optimal treatment time of this conversion coating was much shorter and the corrosion resistance was obviously improved. The effect of Mn 2+ on the formation of golden Ti/Zr conversion coating was thoroughly investigated by means of energy dispersive X‐ray spectroscopy, SEM, XPS, and Raman and electrochemical workstation. The results showed that the conversion coating had a double‐layer structure: the outer layer consisted of the metal‐organic complex and the inner layer was mainly made up of Na 3 AlF 6 . Mn 2+ was oxidized into MnOOH in solution and precipitated on the substrate surface which provided the nucleus to Na 3 AlF 6 crystal and accelerated Na 3 AlF 6 crystal formation and also made the microstructure of conversion coating change to the cubic. The mechanism of the formation of the conversion coating can be deemed as nucleation, growth of Na 3 AlF 6 crystal, and formation of metal‐organic complex. Copyright © 2015 John Wiley & Sons, Ltd.