Hydroxyapatite coating of AZ31 magnesium alloy by a solution treatment and its corrosion behavior in NaCl solution
Hydroxyapatite coating of AZ31 magnesium alloy by a solution treatment and its corrosion behavior in NaCl solution
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DOI：
10.1016/j.surfcoat.2011.04.036
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发表时间：
2011-06-25
影响因子：
5.4
通讯作者：
Tomozawa, Masanari
中科院分区：
文献类型：
--
作者：
Hiromoto, Sachiko;Tomozawa, Masanari
在250 mmol/L的C10 H12 N2 O 8 Na 2Ca水溶液（pH 8.9）中，在AZ 31镁合金和纯镁表面直接制备了羟基磷灰石（HAp）涂层。处理时间从2 h变化到6 h。结晶相。研究了涂层的形貌和组成。在3.5wt.% NaCl溶液中的腐蚀行为进行了研究羟基磷灰石涂层试样。热处理时间较短的AZ 31镁合金HAp涂层存在缺陷，随着热处理时间的延长，涂层缺陷逐渐减少。AZ 31镁合金的HAp涂层由致密的内层和粗糙的外层组成，与纯镁涂层相似。AZ 31镁合金的内层由密集堆积的圆顶状析出相组成。外层由从每个圆顶径向生长的棒状晶体组成。内层HAp的（002）面和棒状晶体大致朝向基底。HAp涂层显著降低了镁离子的析出量和腐蚀电流密度。这些值中的每一个在HAp涂覆的AZ 31和纯Mg之间处于相同的数量级。随着处理时间的延长，AZ 31的离子释放量略有下降。AZ 31的原始内部致密层在浸泡后保留。结果表明，HAP涂层的保护作用主要集中在内层，与基体的种类无关。(C)2011 Elsevier B. V.保留所有权利。
Hydroxyapatite (HAp) coatings were formed directly on AZ31 magnesium alloy and pure Mg in a 250 mmol/L C10H12N2O8Na2Ca aqueous solution of pH 8.9. Treatment time was varied from 2 h to 6 h. Crystal phase. morphology and composition of the coatings were investigated. Immersion and polarization tests in a 3.5 wt.% NaCl solution were performed to examine the corrosion behavior of the HAp-coated specimens. The HAp coating of AZ31 with short treatment time had defects which decreased with an increase in treatment time. The HAp coatings of AZ31 consisted of an inner dense layer and an outer coarse layer in the similar manner for pure Mg. The inner layer on AZ31 was composed of dome-shape precipitates densely packed. The outer layer was composed of rod-like crystals growing from each dome in the radial direction. The (002) plane of HAp of inner layer and rod-like crystals roughly oriented to the substrate. Magnesium ion-release and corrosion current density were remarkably reduced with HAp coatings. Each of these values was on the same order of magnitude between HAp-coated AZ31 and pure Mg. The ion release from AZ31 slightly decreased with an increase in treatment time. The original inner dense layer of AZ31 remained after the immersion. It is suggested that the protectiveness of HAP coating relays on the inner layer and does not significantly depend on the kind of Mg substrate. (C) 2011 Elsevier B.V. All rights reserved.