Structure and corrosion resistance of modified micro-arc oxidation coating on AZ31B magnesium alloy

A hydrophobic surface was fabricated on a micro-arc oxidation (MAO) treated AZ31 Mg alloys via surface modification with myristic acid. The effects of modification time on the wettability of the coatings were investigated using the contact angle measuring device. The surface morphologies and structu...

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Bibliographic Details
Published in:Transactions of Nonferrous Metals Society of China 2016-03, Vol.26 (3), p.814-821
Main Authors: CUI, Xue-jun, YANG, Rui-song, LIU, Chun-hai, YU, Zu-xiao, LIN, Xiu-zhou
Format: Article
Language:English
Subjects:
Coating
Contact angle
Corrosion resistance
hydrophobicity
magnesium alloys
Magnesium base alloys
micro-arc oxidation
myristic acid
Oxidation
plasma electrolytic oxidation
Protective coatings
Surface energy
Wettability
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Summary:A hydrophobic surface was fabricated on a micro-arc oxidation (MAO) treated AZ31 Mg alloys via surface modification with myristic acid. The effects of modification time on the wettability of the coatings were investigated using the contact angle measuring device. The surface morphologies and structure of the coatings were evaluated using SEM, XRD and FT-IR. The corrosion resistance was investigated by potentiodynamic polarization curves and long-term immersion test. The results showed that the water contact angle (CA) increases gradually with modification time from 0 to 5 h, the highest CA reaches 138° after being modified for 5 h, and the number and size of the micro pores are decreased. The modification method hardly alters crystalline structure of the MAO coating, but improves the corrosion resistance based on the much positive potential and low current density. Moreover, the corrosion resistance and hydrophobicity can be enhanced with increasing the alkyl chain. The wetting and spreading for the alkylcarboxylate with low surface energy become easier on the micro-porous surface, and alkylcarboxylate monolayer will be formed through bidentate bonding, which changes the surface micropores to a sealing or semi-sealing structure and makes the MAO coating dense and hydrophobic. All the results demonstrate that the modification process improves the corrosion protection ability of the MAO coating on AZ31B Mg alloy.
ISSN:1003-6326
DOI:10.1016/S1003-6326(16)64172-9