An investigation of new barium phosphate chemical conversion coating on AZ31 magnesium alloy
An investigation of new barium phosphate chemical conversion coating on AZ31 magnesium alloy
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DOI：
10.1016/j.surfcoat.2012.09.009
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发表时间：
2012-10-15
影响因子：
5.4
通讯作者：
Bensebaa, Farid
中科院分区：
文献类型：
--
作者：
Chen, Yougui;Luan, Ben Li;Bensebaa, Farid
磷酸钡化学转化膜是镁合金防腐蚀的一个新的研究领域。本文报道了一种以Ba（NO_3）（2）和NH_4H_2PO_4为前驱体的简单溶液体系中的新工艺。研究了镀液pH值、温度、Ba（NO3）2和NH4H2PO4浓度以及沉积时间对镀层性能的影响。所获得的涂层典型地以两层结构为特征。然后用扫描电子显微镜（SEM）、能量色散X射线能谱（EDX）、X射线光电子能谱（XPS）和X射线衍射（XRD）对化学组成和结构进行进一步表征，揭示了混合无定形磷酸盐的下层和结晶BaHPO4的上层。通过电化学极化曲线比较了裸镁合金和涂层镁合金的耐蚀性，结果表明涂层镁合金的耐蚀性得到了提高。更具体地，双层涂层显示出比单独使用下层涂层更有效。此外，还进行了附着力测试，以评估涂层的结合强度并确定分离界面。皇冠版权所有（C）2012由Elsevier B.V.出版。保留所有权利。
Barium phosphate chemical conversion coating is a new research area for the corrosion protection of Mg alloys. We report a new process conducted in a simple solution with Ba(NO3)(2) and NH4H2PO4 as the precursors. The influences of pH value and temperature of the coating bath, concentrations of Ba(NO3)(2) and NH4H2PO4, and deposition time were evaluated. The coating obtained typically featured a two-layer structure. The chemical compositions and structures were then further characterized with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), revealing an under layer of mixed amorphous phosphates and a top layer of crystalline BaHPO4. The corrosion resistances of bare Mg alloy and those with coatings were compared with electrochemical polarization, showing an improved corrosion resistance of samples with coating. More specifically, the two-layer coating was shown to be more effective than with the under layer coating alone. In addition, adhesion test was also conducted to evaluate the bonding strength and to identify the separation interface of the coatings. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.