Study of surface color change of LZ91 magnesium alloy through processes of micro arc oxidation
Date Issued
2014
Date
2014
Author(s)
Lin, Yu-Ting
Abstract
Magnesium alloys have good physical properties. Unfortunately, magnesium alloys exhibit a very poor corrosion resistance, wear and color of surface. These weak points will seriously influence their future development and applications. Micro arc oxidation technology, which generates on the alloy surface to develop ceramic-like oxide coatings,is one of the new surface treatments for magnesium alloys. It can remarkably promote the corrosion, wear resistance and change surface color.
In this study, effects of various electrolytic compositions and oxidation times on the color change of MAO coatings of LZ91 magnesium alloys were evaluated. Phytic
acid, which exhibits powerful chelating capability with di- and trivalent cations, is a main electrolytic composition in this study. Furthermore, some CuSO4·5H2O or KMnO4
is combined with phytic acid to further improve the oxide-coating color, wear and corrosion resistance. The colorimeter, SEM, XRD, XPS, potentiodynamic polarization, EIS, salt spray, pin-on-disk tribo-meter are used to analyze the MAO surface
morphologies, coating colors, wear and corrosion properties.
In this work, the growth rate of oxide coating in phytic acid is fast. The surface coating in phytic acid exhibits a gray color and could improve the corrosion properties
of LZ91 magnesium alloys. However, the oxide coating in phytic acid is not dense sufficiently and will be penetrated easily by corrosion atmosphere after a long period
in corrosion environment. On the other hand, addition of CuSO4·5H2O or KMnO4 causes coating color to exhibit 70% dim gray or camel, respectively. But the growth rate of oxide coating decreases and the wear and corrosion resistance are reduced.
Based on these experimental results, the electrolyte of phytic acid with suitable content of CuSO4‧5H2O or KMnO4 with phytic acid will change the colors of thin film,which properties of film will not be affected.
Subjects
鎂合金
微弧氧化
植酸
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-103-R01527019-1.pdf
Size
23.54 KB
Format
Adobe PDF
Checksum
(MD5):590bfbe10254f49dba98ec470463c1d5