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概述了镁合金化学镀镍前处理的工艺流程(包括酸洗、活化和一步酸洗活化)、制取中间层方法(包括浸锌/铝、预镀、化学转化膜和微弧氧化)的研究现状,以及化学镀镍工艺在主盐、镀液配方、工艺条件等方面的研究进展. 相似文献
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采用划叉浸泡实验,电化学交流阻抗(electrochemical impedance spectroscopy,EIS),开路电位(open circuit potential,OCP)及动电位扫描研究了不同类型的环氧树脂对于AZ91D镁合金的表面的富镁涂层的保护性能的影响。结果表明环氧618-593构成的富镁涂层防护性能较差;环氧6101-TY650制备的富镁涂层可明显改善涂层对破损处镁合金基体的保护作用,但涂层本身长期防护性能较差;环氧618-T31构成的富镁涂层对AZ91D镁合金的防护作用较强,适宜制备镁合金表面的富镁涂层。3种环氧涂料中加入镁粉颗粒制备的富镁涂层均可对缺陷处裸露的AZ91D镁合金基体提供保护,从而延长漆膜的破坏时间。涂层中的镁粉颗粒被激活后,为镁合金的基体提供了一定程度的阴极保护作用,减缓了镁合金基体的腐蚀。 相似文献
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A double-layer coating was prepared on AZ91D alloy by plasma electrolytic oxidation (PEO) plus electroless plating (EP). The plasma eletrolytic oxidation film was prepared in a silicate bath as an inner layer of the coating. Electroless plated Ni-P layer grew from the pores of the PEO film in a nickelous acetate bath and formed as the outer layer of the coating. The microstructure and crystallographic structure was observed with FESEM and XRD. The corrosion resistance of the double-layer coating was evaluated by means of chronopotentiometric (E-t), potentiodynamic polarization (E-i), neutral salt spray test and electrochemical impedance spectroscopy (EIS) test. Compared with the data of as-cast AZ91D magnesium, the open circuit potential of the double-layer coated AZ91D alloy increased by 1.1815 V, while the self-corrosion current density decreased by two orders of magnitude. E-i, EIS result showed that the corrosion resistance of magnesium alloy AZ91D was improved by the double-layer coating. The salt spray test and polarization test results show that the pitting corrosion resistance of AZ91D alloy was improved greatly. An equivalent circuit was proposed to fit the impedance diagrams of AZ91D alloy with the coating. 相似文献
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针对汽车用AZ91D镁合金耐蚀性不佳的问题,采用镀覆方法对其表面进行改性。采用特殊方法对镁合金进行预处理,并对表面改性的镁合金的耐蚀性进行研究。结果表明:腐蚀初期,镀层能够保护镁合金基体免遭腐蚀,有效提高镁合金基体的耐蚀性;腐蚀后期,镀层对镁合金基体的保护作用被削弱。 相似文献
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High corrosion protection of a polyaniline/organophilic montmorillonite coating for magnesium alloys
Epoxy coatings containing polyaniline (PANI) and polyaniline/organophilic montmorillonite (PANI/OMMT) powders were prepared on the surface of AZ91D magnesium alloy. The corrosion performance of the coatings was evaluated by electrochemical impedance spectroscopy (EIS) and open-circuit potential analysis in 3.5% NaCl. The results indicate that the PANI/OMMT coating retained its high corrosion protection for AZ91D magnesium alloy after 6000 h of immersion. The protective mechanism conferred by the PANI/OMMT coating was also discussed. The effects of oxygen on the protective mechanism of PANI were evaluated by EIS measurements in a 3.5% deaerated NaCl solution. 相似文献
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为改善和提高汽车支架类零件常用的AZ91D镁合金表面耐蚀性能,采用两步法在其表面电沉积Ni-SiO_2复合镀层。设计了正交试验,以SiO_2质量分数和表面粗糙度作为评价指标,运用正交试验法确定了施镀工艺参数的影响主次顺序,并得到最优施镀工艺参数为:镀液中SiO_2颗粒质量浓度20 g/L、电流密度8 A/dm~2、超声波功率300 W、镀液温度55℃。结果表明:采用最优施镀工艺制备出Ni-SiO_2纳米复合镀层,其表面平整、致密,腐蚀均匀,腐蚀速率为65 g/(m~2·d),明显低于镁合金基体的96 g/(m~2·d)。Ni-SiO_2纳米复合镀层能够提供有效的表面防护,改善和提高镁合金耐蚀性能。 相似文献
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This study evaluated the corrosion resistance of AZ91D magnesium alloy coated by composite coatings which consisted of a molybdate conversion coating and three layers of silicon sol–gel coatings. For molybdate conversion treatment, various conditions including the pH of the molybdate baths, immersion time and bath temperature were investigated using electrochemical measurements. The corrosion resistance of the AZ91D magnesium alloy was improved to some extent by the conversion coating with the optimal conversion parameters (7.3 g/L (NH4)6Mo7O24·6H2O solution with pH 5 for 30 min at 30 °C). 相似文献
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在AZ 91D镁合金基体上分别制备三元化学镀Ni-Cu-P,Ni-Ce-P镀层,用失重法将试样分别放入质量分数为3.5%的NaCl溶液和质量分数为5%的醋酸溶液中进行耐蚀性对比实验。结果表明:相对于AZ 91D基体,Ni-Cu-P镀层和Ni-Ce-P镀层在质量分数为5%的醋酸溶液中耐蚀性分别提高了50倍和12.8倍,在质量分数为3.5%的NaCl溶液中分别提高了2.76倍和91.63倍;经封孔和热处理封孔后的耐蚀性均有明显提高。实验表明:在AZ 91D镁合金表面化学沉积Ni-Ce-P镀层的综合耐蚀性能优于化学沉积Ni-Cu-P镀层的。该实验有助于解决镁合金的耐蚀性问题、提高其表面性能和拓宽其应用前景。 相似文献