镁合金涂装前处理的试验研究

发布时间：2019-04-16 19:37

【摘要】：镁是继钢铁、铝之后的第三大金属工程材料,被誉为“21世纪绿色工程材料”,具有许多优良的性能,通常以镁合金型材的形式使用,应用前景极为广泛。镁合金型材主要应用在化学化工、电子工业、交通工具、航空航天工业等行业。目前镁合金型材防腐所使用的技术比较落后,主要有铬酸处理及非铬酸处理两种方法。铬酸处理因其处理时间短、温度高、浓度高而具有操作难度大、成本高、污染严重等缺点。非铬酸处理技术不成熟。本课题在实际试用过程中,已经克服了以上缺点,找到了一个经济、环保操作条件温和,对材料适应性广,通用性强的处理办法。本课题通过试验研究了镁合金(AZ91)的化学氧化和电化学氧化两种成膜机理及其质量影响因素。其中,用Cr O3(5g/L)、Ca SO4(5g/L),室温处理2min,得到镁合金化学氧化膜,对其电化学腐蚀性能进行表征,结果表明:该膜的自腐蚀电位为-1.358V;用200g/LCr O3、20g/L Ca SO4、30g/LNa NO3处理2min,自腐蚀电位为-1.461V。低浓度铬酸氧化也可达到高浓度氧化的抗腐蚀效果,产品满足GB6807-2001和GB6807-86标准,被氧化的镁合金经静电喷涂75μm环氧/聚酯粉末涂料,其附着力、盐雾试验均满足正常使用。孔隙率经检测达到5%左右。铬酸盐氧化镁合金做涂装前处理,具有经济适用和自修复的特点,废水经处理后可达到排放标准。近年来,水污染形势严峻,一些地方严格禁止使用污染严重的六价铬,为此本课题进行了非铬的电化学氧化研究。预处理的镁合金,在80~85℃下,电化学氧化液组成为280 g/L的Na OH、36 g/L的Na2Si O3、4 g/L的苯酚氧化9~10min,所得膜。表面光洁完整,自腐蚀电位为-1.440V,孔隙率≤70%,封闭后可以满足涂装前处理要求。涂装后根据国标GB/T 9286-88规定,采用划格法测试,附着力为“0-1”级。根据国标GB/T 1771-1991进行漆膜耐盐雾试验,测试结果:35℃下120小时无腐蚀现象产生。漆膜耐湿热性测定,根据GB/T1740-1979测定,96小时后漆膜无气泡、开裂等现象。研究结果表明:本课题确定的镁合金成膜方法可以实现处理液低浓度和低温度,通过延迟处理时间和降低腐蚀速度来提高漆膜稳定性并降低成本的目的。方法为大型镁合金型材的涂装前处理工程化奠定了基础。
[Abstract]:Magnesium is the third largest metal engineering material after steel and aluminum. It is known as "green engineering material in the 21st century", and has many excellent properties. It is usually used in the form of magnesium alloy profiles, and its application prospect is very wide. Magnesium alloy profiles are mainly used in chemical and chemical industry, electronic industry, transportation tools, aerospace industry and other industries. At present, the anti-corrosion technology of magnesium alloy profiles is backward, mainly chromic acid treatment and non-chromic acid treatment. Chromic acid treatment is difficult to operate, high cost and serious pollution due to its short treatment time, high temperature and high concentration. Non-chromic acid treatment technology is not mature. In the process of practical trial, this subject has overcome the above shortcomings, and found an economic, environmental protection, mild operating conditions, wide adaptability to materials, strong versatility. In this paper, the mechanism of chemical oxidation and electrochemical oxidation of magnesium alloy (AZ91) and the influencing factors of its quality were studied. Cr O 3 (5g/L), Ca SO4 (5g/L) was used to prepare the chemical oxidation film of magnesium alloy at room temperature for 2 min. The electrochemical corrosion properties of the film were characterized. The results showed that the corrosion potential of the film was-1.358V, and the corrosion potential of the film was-1.358V. When treated with 200g/LCr O3, 20g / L Ca SO4,30g/LNa NO3 for 2 min, the self corrosion potential was-1.461V. Low concentration chromic acid oxidation can also achieve the high concentration oxidation anti-corrosion effect, the product meets the GB6807-2001 and GB6807-86 standard, the oxidized magnesium alloy by electrostatic spraying 75 渭 m epoxy / polyester powder coating, its adhesion, salt spray test meet the normal use. The porosity was about 5%. The pretreatment of chromate magnesium oxide alloy has the characteristics of economical application and self-repair, and the waste water can meet the discharge standard after treatment. In recent years, the situation of water pollution is serious, and the use of heavily polluted hexavalent chromium is strictly prohibited in some places. Therefore, the electrochemical oxidation of non-chromium has been studied in this paper. The pre-treated magnesium alloy was prepared by electrochemical oxidation of 280g / L Na OH,36 / g / L Na2Si-O3 and 4g / L phenol for 9min at 80 ~ 85 鈩，

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