【摘要】：鎂合金因具有低密度、高強度、高剛性、和較強的消震性及韌性等優(yōu)異性能,而廣泛用于國防、航空航天、運輸、電子領域等,在機械零件制造領域,甚至有望取代鋁和鋼。但是,鎂合金的耐腐蝕性差、化學反應活性高,限制了它在工業(yè)生產(chǎn)中的更廣泛應用。本文將制備好的化學鍍鎳層浸入質量分數(shù)為3.5%的NaCl溶液中浸泡,對鍍層做初步評估。鍍層與基底間的結合力用GB/T 5270—2005和ISO 2819推薦的劃線和劃格試驗方法進行測定。實驗采用掃描電子顯微鏡(SEM,Hitachi S-4800,日本)表征鍍層的表面及截面形貌。用X射線能譜儀(EDX,Horiba,EX-350)進行鍍層成分分析。鍍層晶形結構使用X射線衍射儀(XRD,D8 Advance,德國)X射線光電子能譜(XPS,PHI5000,Versaprobe)測定。將制備好的鍍層浸泡在一定濃度的NaCl溶液中,用電化學測試方法對鎂合金上的鍍層的腐蝕電位Ecorr,腐蝕電流ic等參數(shù)進行了測試。通過實驗和討論,得到如下結論:(1)研究了一種制備高耐蝕納米復合鍍層的方法——兩步化學鍍。采用兩步化學鍍方法,在AZ31鎂合金最外層鍍層中引入二氧化硅納米顆粒(NSPs),會形成一種功能化復合涂層,使鍍層的表面更平滑,均勻,并且具有很強的耐腐蝕性能。NSPs的摻入不會對復合鍍層Ni-P/Ni-P-nano-SiO2(NNNS)的晶態(tài)結構產(chǎn)生影響,整體鍍層都保持非晶態(tài)結構。最佳鍍層在NaCl溶液中的緩蝕效果高于HCl溶液。新制備的鍍層性能提高的主要原因是涂層缺陷的錯位和腐蝕過程中NSPs的“屏障效應”。(2)研究了鎂合金上均勻分散F@MSNs(Mesoporous Si nanocontainers)的具有自愈功能的鎳涂層的制備。所制備的F@MSNs鍍層具有良好的耐腐蝕性能的原因為F@MSNs釋放的氟離子與鎂離子之間發(fā)生反應生成了MgF2保護膜。氟離子的釋放和MgF2薄膜的形成可以有效的修復鎂合金表面的自然氧化膜缺陷,從而改變腐蝕機理并且降低鎂合金的腐蝕速率。鎂合金浸泡在腐蝕介質中,隨著時間的增大,腐蝕電位Ecorr趨向穩(wěn)定,腐蝕電流ic減小,電極阻抗Rp增大都可以進一步證實納米復合鍍層的自愈功能。
[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.
【學位授予單位】：西華師范大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG174.44

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