镁合金高耐蚀化学镀镍层的防护研究

发布时间：2018-07-22 11:47

【摘要】：镁合金因具有低密度、高强度、高刚性、和较强的消震性及韧性等优异性能,而广泛用于国防、航空航天、运输、电子领域等,在机械零件制造领域,甚至有望取代铝和钢。但是,镁合金的耐腐蚀性差、化学反应活性高,限制了它在工业生产中的更广泛应用。本文将制备好的化学镀镍层浸入质量分数为3.5%的NaCl溶液中浸泡,对镀层做初步评估。镀层与基底间的结合力用GB/T 5270—2005和ISO 2819推荐的划线和划格试验方法进行测定。实验采用扫描电子显微镜(SEM,Hitachi S-4800,日本)表征镀层的表面及截面形貌。用X射线能谱仪(EDX,Horiba,EX-350)进行镀层成分分析。镀层晶形结构使用X射线衍射仪(XRD,D8 Advance,德国)X射线光电子能谱(XPS,PHI5000,Versaprobe)测定。将制备好的镀层浸泡在一定浓度的NaCl溶液中,用电化学测试方法对镁合金上的镀层的腐蚀电位Ecorr,腐蚀电流ic等参数进行了测试。通过实验和讨论,得到如下结论:(1)研究了一种制备高耐蚀纳米复合镀层的方法——两步化学镀。采用两步化学镀方法,在AZ31镁合金最外层镀层中引入二氧化硅纳米颗粒(NSPs),会形成一种功能化复合涂层,使镀层的表面更平滑,均匀,并且具有很强的耐腐蚀性能。NSPs的掺入不会对复合镀层Ni-P/Ni-P-nano-SiO2(NNNS)的晶态结构产生影响,整体镀层都保持非晶态结构。最佳镀层在NaCl溶液中的缓蚀效果高于HCl溶液。新制备的镀层性能提高的主要原因是涂层缺陷的错位和腐蚀过程中NSPs的“屏障效应”。(2)研究了镁合金上均匀分散F@MSNs(Mesoporous Si nanocontainers)的具有自愈功能的镍涂层的制备。所制备的F@MSNs镀层具有良好的耐腐蚀性能的原因为F@MSNs释放的氟离子与镁离子之间发生反应生成了MgF2保护膜。氟离子的释放和MgF2薄膜的形成可以有效的修复镁合金表面的自然氧化膜缺陷,从而改变腐蚀机理并且降低镁合金的腐蚀速率。镁合金浸泡在腐蚀介质中,随着时间的增大,腐蚀电位Ecorr趋向稳定,腐蚀电流ic减小,电极阻抗Rp增大都可以进一步证实纳米复合镀层的自愈功能。
[Abstract]:Magnesium alloys have excellent properties such as low density, high strength, high rigidity, strong earthquake resistance and toughness, and are widely used in national defense, aerospace, transportation, electronics and so on. In the manufacturing field of mechanical parts, it may even replace aluminum and steel. However, the corrosion resistance of magnesium alloys is poor and the chemical reaction is high, which restricts its industrial production. More widely used. In this paper, the prepared electroless nickel coating was soaked in a NaCl solution with a mass fraction of 3.5%. A preliminary evaluation of the coating was made. The binding force between the coating and the substrate was measured by the line and the lattice test recommended by GB/T 5270 - 2005 and ISO 2819. The experiments were made of scanning electron microscopy (SEM, Hitachi S-4800, Japan). The surface and cross section morphology of the coating. Analysis of the composition of the coating with the X ray spectroscopy (EDX, Horiba, EX-350). The crystalline structure of the coating is measured by the X ray photoelectron spectroscopy (XPS, PHI5000, Versaprobe) by the X ray diffractometer (XRD, D8 Advance, Germany). The prepared plating layer is soaked in a certain concentration of solution, and the electrochemical testing method is used. The corrosion potential Ecorr and corrosion current IC of the coating on magnesium alloy have been tested. Through experiments and discussions, the following conclusions have been obtained: (1) a method of preparing high corrosion resistant nanocomposite coatings was studied by two steps of electroless plating. By two steps of electroless plating, silicon dioxide nanoparticles (NS) were introduced into the outer layer of the AZ31 magnesium alloy. Ps), a functional composite coating will be formed to make the surface of the coating more smooth and uniform, and the addition of.NSPs with strong corrosion resistance will not affect the crystalline structure of the composite coating Ni-P/Ni-P-nano-SiO2 (NNNS). The whole coating keeps the amorphous structure. The corrosion inhibition effect of the best coating in the NaCl solution is higher than that of the HCl solution. The main reasons for improving the performance of the deposited coating are the dislocation of the coating defects and the "barrier effect" of NSPs during the corrosion process. (2) the preparation of a self-healing nickel coating on the magnesium alloy F@MSNs (Mesoporous Si nanocontainers) is studied. The reason for the good corrosion resistance of the prepared F@MSNs coating is F@MSNs. The release of fluorine ions and the magnesium ion formed the MgF2 protective film. The release of fluorine ions and the formation of MgF2 film can effectively repair the natural oxide film defects on the surface of the magnesium alloy, thus change the corrosion mechanism and reduce the corrosion rate of the magnesium alloy. The Ecorr tends to be stable, the corrosion current IC decreases, and the impedance Rp increases, which can further confirm the self healing function of the nanocomposite coating.
【学位授予单位】：西华师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.44

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