Surface treatment of magnesium alloys by artificial corrosion-oxidization method : Special issue on platform science and technology for advanced magnesium alloys, II
Surface treatment of magnesium alloys by artificial corrosion-oxidization method : Special issue on platform science and technology for advanced magnesium alloys, II
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人工腐蚀-氧化法镁合金表面处理：先进镁合金平台科学与技术专刊II
DOI：
10.2320/matertrans.44.511
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
H. Tsubakino
中科院分区：
文献类型：
--
作者：
A. Yamamoto;H. Tsubakino
提出了一种改善镁及其合金耐腐蚀性差的新技术。将样品浸入高pH值溶液中，例如10% NaOH、(1% NaCl + 10% NaOH)和(10% NaCl + 10% NaOH)溶液，在室温下浸泡3.6 ks，然后在空气中在673-773 K下热处理3.6 ks。试样的耐腐蚀性通过在使用1% NaCl溶液的盐浸试验中发生丝状腐蚀的时间t f 来评价。通过腐蚀氧化处理，抑制了盐浸试验初期的氢泡产生，并且通过该处理延长了t f 。在未经处理的AZ31合金样品上，t f 约为1.7 ks，而在仅在空气中于673 K下热处理而没有初次浸泡的样品上，t f 约为1.9 ks。另一方面，当使用（10% NaCl + 10% NaOH）溶液进行初次浸泡，然后在空气中于 673 K 下加热 3.6 ks 时，t f 延长至约 35 ks，比未处理的样品长约 20 倍。据认为，通过一次浸泡处理在试样表面形成的氢氧化镁转变为氧化镁，从而保护了试样免受腐蚀。通过TEM观察证实了在经过腐蚀氧化法处理并加热而不进行一次浸泡的样品的两个表面上形成了氧化镁。两个氧化物层的微观结构彼此不同，直接由金属镁形成的氧化物的内聚力似乎比由氢氧化镁形成的氧化物的内聚力弱。
A new technique has been proposed for improving the poor corrosion resistance in magnesium and its alloys. The specimens were immersed into solutions with high pH values, such as 10% NaOH, (1% NaCl + 10% NaOH) and (10% NaCI + 10% NaOH) solutions, at R. T. for 3.6 ks, and then heat treated in air at 673-773 K for 3.6 ks. Corrosion resistance of the specimens were evaluated by the time for occurring filiform corrosion, t f , in salt immersion test using 1% NaCl solution. Hydrogen bubble evolution at the early stage of the salt immersion test was suppressed by the corrosion-oxidization treatment, and also t f was prolonged by this treatment. On the non-treated specimen of AZ31 alloy, t f was about 1.7 ks, and on the specimen only heat-treated in air at 673 K without the primary immersion, t f was about 1.9 ks. On the other hand, when the (10% NaCI + 10% NaOH) solution was used for the primary immersion and then heated in air at 673 K for 3.6 ks, t f was prolonged up to about 35 ks, about 20 times longer than that in the non-treated specimen. It is considered that magnesium hydroxide formed on the surface of the specimen by the primary immersion treatment changed into magnesium oxide which protected the specimen from corrosion. Formation of magnesium oxide on both the surfaces of the specimens treated by the corrosion-oxidization method and heated without the primary immersion was confirmed by TEM observations. Microstructures in both the oxide layers were different one another, cohesion of the oxide formed directly from metallic magnesium seemed to be weak compared with that formed from magnesium hydroxide.