飞机结构铝合金直接化学镀Ni-P合金研究

高强度铝合金被广泛用于飞机结构中,然而,这一系列铝合金抗腐蚀和耐磨性差,限制了其应用。而Ni-P合金镀层具有高的硬度和抗腐蚀性能等优异特点,成为增强表面性能的常用手段。采用化学镀镍工艺在铝合金（6061）表面进行化学镀镍处理,研究了pH值、沉积温度和沉积时间对沉积速率的影响。分析了化学镀镍层的成分和组织形貌,同时对镀层的硬度、抗腐蚀性进行了表征。试验表明,在铝合金表面化学镀镍可以显著提高铝合金表面的硬度,并改善其在5％NaCl溶液中的耐蚀性。     

Electroless Ni-P layer with a chromium-free pretreatment on AZ91D magnesium alloy

A phosphate-manganese conversion film was proposed as the pretreatment layer between Ni-P coating and AZ91D magnesium alloy substrate, to replace the traditional chromium oxide plus HF pretreatment. The subsequent Ni-P deposited on the layer was also characterized by its structure, morphology, microhardness and corrosion-resistance. The pretreatment layer on the substrate not only reduces the corrosion of magnesium during Ni-P plating process, but also reduces the potential difference between the matrix and the second phase. Thus, a Ni-P coating with fine and dense structure was obtained on the AZ91D magnesium alloy, which shows better corrosion resistance than the Ni-P with chromium oxide plus HF as pretreatment.     

中温酸性化学镀镍磷合金组织和性能研究

化学镀成本高是影响其应用的原因之一.降低化学镀工艺温度及其镀液配制成本是降低化学镀成本的有效途径.对自来水配制的中温酸性化学镀镀液进行了周期试验,并对镀层表面成分、组织、性能进行了研究.结果表明:研制的配方及工艺具有镀速稳定、允许负载大(≤2.2dm2/L)和寿命长(≥8个周期)等特点.镀层表面含磷量与化学镀时间有关.镀层具有较高的硬度、良好的耐蚀性,且与基体结合力良好.因此,研制的镀液有望获得应用.     

沉积时间对镁合金表面化学镀镍磷合金的影响

沉积时间是影响化学镀镍磷合金最重要的工艺参数之一。采用不同施镀时间在AZ31镁舍金表面进行化学镀镍磷合金,分析了这一主要工艺参数对镀层的硬度、沉积速率、耐腐蚀性、微结构及形貌等的影响,拟对这6．5,温度为85℃的条件下,选择施镀持续时间为45min时镀层质量最佳,所得镀层光亮,胞状一主要工艺参数进行优化,为AZ31镁合金的表面处理提供依据。结果表明：在镀液pH值为组织均匀致密,耐腐蚀性比基体明显有所提高,并具有较高的硬度。     

镁合金表面化学镀Ni-P合金研究

镁是一种极活泼的金属,其合金具有优异的性能,是得到广泛应用的重要原因.然而,镁合金在各介质中的不耐蚀,其应用受到了制约.据文献报道,已有多种方法被应用到镁合金上,但效果都不很理想;而化学镀镍技术是近年来发展较快的一种表面处理方法.进一步探讨了在AZ91D表面上进行化学镀镍的研究过程:通过多次试验确定了镁合金的前处理方案,研究了在酸性条件下镁合金表面直接化学镀镍的一套工艺路线,配置简单,操作方便,避免了预镀中间层的麻烦.并且测定了镀层的厚度、显微硬度,观察了镀态的金相组织;热震实验和划痕实验的结果表明镀层与衬底具有良好的结合力.     

Electroless Ni-Sn-P coating on AZ91D magnesium alloy and its corrosion resistance

An electroless Ni-Sn-P coating was deposited on AZ91D magnesium alloy in an alkaline-citrate-based bath where nickel sulphate and sodium stannate were used as metal ion sources and sodium hypophosphite was used as a reducing agent. The phase structure of the coating was amorphous. SEM and attached EDS observation revealed the presence of dense and uniform nodules in the ternary coating and the content of tin was 2.48wt.%. Both the electrochemical analysis and the immersion test in 10% HCl solution proved that the ternary Ni-Sn-P coating exhibited better corrosion resistance than the Ni-P coating in protecting the magnesium alloy substrate.     

A study of chromium-free pickling process before electroless Ni-P plating on magnesium alloys

A chromium-free pickling process of magnesium alloys in H₃PO₄ + Na₂MoO₄ solution for electroless Ni-P plating was described. The dosage of Na₂MoO₄ was established by detecting adhesion and corrosion resistance of chemical nickel coatings. Electrochemical behaviors of pickling solution of H₃PO₄ + Na₂MoO₄ and NH₄HF₂ activation solution were investigated with the open circuit potential curves and the polarization curves. The results show that the Na₂MoO₄ has strong inhibition ability. Na₂MoO₄ in H₃PO₄ solution can reduce active sites of microcathodic and microanodic zones in the corrosion cells of the substrate surface of magnesium alloys and plays an inhibition role. The activation film with some oxides and fluorides can prevent the substrate magnesium from the fierce displacement and corrosion reaction of electroless plating bath. The chemical Ni-P coating with good adhesion and corrosion resistance was obtained by the pretreatment of 200 cm³ dm⁻³ 85% H₃PO₄ + 5 g dm⁻³ Na₂MoO₄ pickling bath and activation in 200 g dm⁻³ NH₄HF₂ solution. This procedure of surface pretreatment before electroless nickel plating can replace the existing acid pickling containing chromium and HF activation.     

彩色化学镀镍磷合金镀层研究

探讨了在钢表面获得彩色化学镀镍层的方法,分析了各种工艺因素对色彩的影响,同时对彩色镀层的耐磨、耐蚀性能也进行了比较.结果表明:用钼酸铵作着色剂,并采用先镀镍,后着色的工艺,通过控制着色处理的工艺参数,可获得不同的色彩,并可保持镀层原有的耐磨、耐蚀性能.最后对形成彩色镀层的机理也进行了初步分析.     

化学镀Ni-P合金添加新工艺的研究

研究了化学镀溶液中镍盐、还原剂、络合剂、稳定剂、氨水的最佳添加量,找到了各种成分最佳的添加量和添加方法,为工业生产提供依据.     

镁合金化学镀Ni-P的工艺研究

由于镁合金在各介质中的不耐蚀性,其应用受到限制.为了在镁合金表面得到保护性镀层,通过多次实验研究镁合金化学镀Ni-P的镀液组成及不同参数对镀速的影响,测定了镀层的显微硬度、结合力和耐蚀性.盐雾实验和显微硬度的结果表明镀层具有较高的耐蚀性和硬度;热震实验和弯曲实验的结果表明镀层与基体具有良好的结合力.综合以上试验结论,试验得出的镁合金化学镀Ni-P层能满足一般工业对其性能的要求.     

镁合金化学镀镍工艺研究

研究了镁合金化学镀镍工艺过程、操作条件,测定了镀层的厚度、显微硬度和结合力,镀层具有较好的耐蚀性.     

有机玻璃化学复合镀(Ni-P)-PTFE工艺

通过实验研究发现：聚甲基丙烯酸甲酯（PMMA,俗称有机玻璃）,经过一系列恰当的预处理如硫磷混酸粗化、化学镀铜等工艺后,可以采用含稳定剂、缓冲剂及四种络合剂配合使用的低温酸性化学复合镀的方法,得到（Ni-P)PTFE镀层,该工艺具有沉积温度低（68－70）℃,镀速高（8－12μm/h),镀液稳定等特点。经镀层性能测试。结果表明：该镀层与基体结合力优异,耐蚀性良好。该工艺成本低廉宜于推广应用。     

SiCp表面化学镀镍合金层的成分与形貌研究

SiCp因其高强度,高模量、耐热、耐磨等优良性能而被作为颗粒增强体制备金属基复合材料。采用优化后的SiCp表面化学镀镍工艺,获得了镍合金包覆SiCp,并对镀镍合金层进行了X－ray衍射成分分析以及镀覆层形貌的SEM考察。结果表明,镀覆层主要为部分非晶态的镍与镍磷合金以及Ni2P的化合物夹杂;粒子的分散很好,结团较少。     

碳钢Ni-P化学镀耐碱性溶液腐蚀性能的研究

为了研究碳钢材料在碱性介质中的腐蚀以及防护方法,采用静态浸泡法以及电化学的方法,对普碳钢以及进行化学镀后的耐碱液腐蚀性能进行了研究.结果表明:普碳钢在室温碱性溶液中放置1h后,表面即发生了严重的腐蚀.在碱性溶液中浸泡24h后,出现了基体局部剥离的现象.普碳钢在碱性溶液中发生了严重的腐蚀.在施加了化学镀层后,普碳钢在碱性溶液中浸泡24h后,表面光洁完整,与未施加化学镀层相比,有很小的腐蚀电流.在碳钢表面施加化学镀层后在碱性介质中具有良好的耐腐蚀性.     

螺杆压缩机转子的化学镀Ni-P合金工艺研究

以材料为QT600-3的螺杆压缩机转子为对象，在实验的基础上，分析化学镀Ni-P合金过程中，络合剂，稳定剂的种类，含量，施镀方式及后处理等对镀层耐蚀性，含磷量，表面形貌等的影响规律。对镀层的物理，化学性能检测结果表明，获得的镀层性能良好。     

pH值对镁合金化学镀Ni-P合金的影响

为进一步确定pH值对镁合金化学镀Ni-P合金的影响,利用扫描电镜(SEM),能谱仪(XPS),显微硬度仪以及极化曲线等方法分析镀层的形貌和性能.结果表明:pH值对镀层的性能影响较大,pH值很低时难于施镀 ,形貌在pH值为8时最好,镀层的含磷量随着pH值的升高而降低;在一定范围内,硬度随着pH值的升高而降低;在pH值为4时,其镀层的自腐蚀电位最高达到-0.92V,耐腐蚀性能最好.     

A study on the electroless Ni-P deposition on WE43 magnesium alloy

In this paper an attempt has been made to understand the mechanism of the deposition process of an electroless Ni-P (EN) coating on WE43 magnesium alloy. Also a number of properties concerning the deposited coatings have been reviewed. The results show that the starting microstructure of the alloy consists of a primary α phase together with some eutectic β phase at triple points and along with some grain boundaries. Microstructural studies reveal an uneven distribution of alloying elements in the phases and they are predominantly segregated to the eutectic β phase. This phenomenon can result in galvanic coupling between eutectic β and primary α phases. Detailed studies prove that the replacement reaction takes place at the early stages of coating, and is followed by the autocatalytic reaction at the next stages of deposition.The X-ray diffraction patterns of primitive coatings show a broad peak around 2θ of 45°, which is an indication of an amorphous or an extremely fine crystalline structure. Annealing at 400 °C for an hour led the nature of deposits to be changed to crystalline phases of Ni, Ni₃P, and NiP₃. Microhardness values of coatings are considerably higher than those of the bare substrate. These further increase when they are annealed at 400 °C for 1 h. Electrochemical polarization curves and calculated corrosion values reveal higher corrosion potential (E_corr) for the coating than for the bare substrate. This decreases again when the coating is annealed at 400 °C for 1 h.     

The corrosion performance of anodised magnesium alloys

The corrosion performance of anodised magnesium and its alloys, such as commercial purity magnesium (CP-Mg) and high-purity magnesium (HP-Mg) ingots, magnesium alloy ingots of MEZ, ZE41, AM60 and AZ91D and diecast AM60 (AM60-DC) and AZ91D (AZ91D-DC) plates, was evaluated by salt spray and salt immersion testing. The corrosion resistance was in the sequential order: AZ91D ≈ AM60 ≈ MEZ ? AZ91D-DC ? AM60-DC > HP-Mg > ZE41 > CP-Mg. It was concluded the corrosion resistance of an anodised magnesium alloy was determined by the corrosion performance of the substrate alloy due to the porous coating formed on the substrate alloy acting as a simple corrosion barrier.     

Formation of an aluminum-alloyed coating on AZ91D magnesium alloy in molten salts at lower temperature

An aluminum-alloyed coating was formed on an AZ91D magnesium alloy in molten salts containing AlCl₃ at a lower temperature of 380 °C. The microstructure and phase constitution of the alloyed layer were investigated by optical microscopy, scanning electron microscopy, energy dispersive spectrum and X-ray diffraction. The nano-hardness of the coating was studied by nanoindentation associated with scanning probe microscopy. The corrosion resistance of the coated specimen was evaluated in a 3.5 wt.% NaCl solution by electrochemical impedance spectroscopy and cyclic potentiodynamic polarization. The results show that the aluminum-alloyed coating consists of Mg₂Al₃ and Mg₁₇Al₁₂ intermetallic layers. The formation of the coating is dictated by the negative standard free energy of the reaction: 2AlCl₃ + 3 Mg = 3MgCl₂ + 2Al. This process is associated with a displacement reaction mechanism and diffusion process that takes place during the molten salt treatment. High activity of Al elements in molten salts contributes to the lower temperature formation of the Al-alloyed coating. The alloyed coating markedly improves the hardness as well as the corrosion resistance of the alloy in comparison with the untreated AZ91D magnesium alloy, which is attributed to the formation of the intermetallic compounds.     

Electroless plating of silver on AZ31 magnesium alloy substrate

Electroless plating of silver on AZ31 magnesium alloys via electroless plating and organic coatings (organosilicon heat-resisting varnish), was studied. The organic coating was made by immersing the samples into organosilicon heat-resisting varnish. The applicability of this method was verified by a subsequent metallization process. In this method the organic coating acted as interlayer between the substrate and silver film. When the reaction started, silver would deposit virtually onto the interlayer surface. X-ray diffraction and SEM analysis were used to investigate the morphology of the interlayer and silver film. The silver film has a rather perfect crystal structure. And the result of the cross-cut test indicates the adhesion between the substrate and interlayer is good enough. The potentiodynamic polarization curves for corrosion studies of the coated magnesium alloys were performed in a corrosive environment of 3.5 wt.% NaCl at neutral pH (7). The result reveals: comparing with the substrate, the corrosion resistance of the coated AZ31 magnesium alloys increases distinctly. Moreover, the silver coating has perfectly antibacterial and decorative properties. The method proposed in this work is environmentally friendly: non-toxic chemicals are used. In addition, it provides a new concept for plating the metals, which are considered difficult to plate due to high reactivity.