针对镁合金阳极氧化膜含有多孔和少量通孔结构，只能提供初期保护效果的问题[1]，有必要解决阳极氧化膜涂层的封孔问题。封孔方法包括：自封孔、沸水封孔、硅酸盐、碱处理和有机高分子涂层[2,3]。碱处理的目的是把氧化镁变成氢氧化镁，体积增大，把孔堵塞；硅烷处理膜层很薄。这两种方法提高MAO膜的耐蚀性能都比较有限。我们这里提出MAO碱处理后，再进行硅烷处理，取得了较好的自愈合耐蚀功效。    

论文“Corrosion resistance of a self-healing microarc oxidation/polymethyltrimethoxysilane composite coating on magnesium alloy AZ31”（镁合金AZ31表面自愈合阳极氧化膜/硅烷复合涂层的耐蚀性）在线发表在腐蚀领域权威期刊《Corrosion Science》(2017, http://dx.doi.org/10.1016/j.corsci.2017.01.025)。

Fig. 1 Schematic representation of the film formation mechanisms of the MAO/PMTMS coating.

Fig. 2 Schematic representation of the corrosion mechanisms of the MAO/PMTMS coating

Highlights

• The MAO/PMTMS coating has a compact morphology with some spherical particles.
  

• The MAO/PMTMS coating (thickness =13.65 μm) possesses a good corrosion resistance.
  

• The PMTMS film acts as a physical and blocking barrier.
  

• The self-healing of PMTMS film plays an important role in its long-term protection.
  

• The PMTMS film peels off due to its swelling and the stress of corrosion products.

 亮点

• 阳极氧化膜/硅烷复合涂层带有球状颗粒，且致密；

• 阳极氧化膜/硅烷复合涂层（13.65 μm厚）具有良好耐蚀性能；

• 硅烷膜起着物理隔离作用；

• 硅烷膜在长期保护过程中具有自愈合的重要作用；

• 硅烷膜由于膨胀和腐蚀产物应力而剥落（失效）。

     Abstract

A micro-arc oxidation (MAO)/polymethyltrimethoxysilane (PMTMS) hybrid coating was fabricated via MAO processing and subsequent sealing with alkaline treatment and PMTMS. The surface morphologies, chemical compositions and corrosion resistances of the coatings were investigated using FE-SEM, FTIR, XRD and electrochemical and hydrogen evolution measurements. The results indicated that the alkaline treatment was beneficial to the silane treatment and that the MAO coating was efficiently sealed by the PMTMS film. The MAO/PMTMS coating significantly enhanced the corrosion resistance of the AZ31 alloy due to its self-healing function. Additionally, we suggest and discuss a corrosion mechanism for the coating.

摘要

镁合金阳极氧化膜经过碱处理和硅烷处理获得阳极氧化膜/硅烷（MAO/PMTMS）复合涂层。通过FE-SEM, FTIR, XRD、电化学和析氢实验研究了该涂层的形貌、化学成份和耐蚀性能。研究结果显示，碱处理有利于硅烷处理和阳极氧化膜被硅烷封孔。MAO/PMTMS膜具有自愈合功能，提高了AZ31镁合金的耐蚀性能。另外，我们提出和讨论了涂层的腐蚀机理。

参考文献：

[1]Lan-Yue Cui, Rong-Chang Zeng*, et al, Degradation mechanism of micro-arc oxidation coatings on biodegradable Mg-Ca alloys- The influence of porosity, Journal of Alloys and Compounds, 695(2017) 2464-2476.

[2] R. C.Zeng, et al,  In vitro corrosion and cytocompatibility of a microarc oxidation coating and poly(L-lactic acid) composite coating on Mg-1Li-1Ca alloy for orthopaedic implants. ACS Applied Materials & Interfaces, 2016, 8 (15): 10014–10028;

[3] R. C.Zeng, et al, In vitro degradation of MAO/PLA coating on Mg-1.21Li-1.12Ca-1.0Y alloy, Front. Mater. Sci., 8 (2014) 343-353.