黄铜化学镀镍磷合金的工艺与性能

研究了黄铜化学镀镍磷合金的工艺。对镀层的成分、结构、结合力和耐腐蚀性进行了分析研究。实验表明:采用酸性镀液施镀,可得到结合力强,磷含量大于12％,非晶态结构的Ni-P合金镀层;并具有优异的耐蚀性。     

磷含量及热处理对化学镀镍磷合金耐蚀性能的影响

研究了磷含量及热处理对化学镀镍磷合金腐蚀行为的影响,结果表明:磷含量对镀层耐蚀性影响很大,磷含量增加,镀层钝化膜形成速率加快,耐蚀性能提高;当磷含量超过8.5％,镀层为非晶态结构,耐蚀性能优异。热处理直接影响了镀层的耐蚀性能,200℃热处理1h,可改善镀层耐蚀性能,温度超过300℃,镀层组织结构发生改变,耐蚀性能降低。     

高稳定性化学镀镍磷合金工艺研究

采用正交试验法研究了络合剂,促进剂,稳定剂以及温度对镀层和溶液性能的影响,从而得到了一种高稳定性的化学镀镍磷合金工艺。该工艺所得镀层磷含量较高,沉积速度快,镀液使用寿命长,并已在工业生产中加以应用。     

化学镀镍磷合金镀层耐蚀性的研究

研究了化学镀镍磷合金镀层的耐蚀性与络合剂、磷含量、热处理温度的关系,并在烟道中进行了挂片实验。     

光亮剂对ZL101铝合金表面化学镀镍磷合金层的影响

研究了在ZL101铝合金表面化学镀Ni-P合金层的结构、显微硬度和耐蚀性.化学沉积Ni-P合金层的主盐是硫酸镍,次亚磷酸钠为还原剂,柠檬酸钠为络合剂.测试了电解液中光亮剂含量对镀层晶体结构、显微硬度和耐蚀性的影响.XRD衍射图谱显示,在所有镀态下Ni-P合金层均为非晶结构,而经过一定温度的热处理后逐渐向晶态转变直至完全晶化.合金镀层的显微硬度值镀态时较低,约为436 HV,随着热处理温度的升高,在400 ℃完全晶化后镀层表面的显微硬度值达到最大,约为1 096 HV.在3.5 wt.% NaCl溶液中测定的动电位极化曲线显示,在铝合金表面化学镀Ni-P合金层具有较好的耐蚀性能.     

航空用铝合金表面化学镀镍磷层的制备及其耐蚀性

为了保证航空铝合金在海洋环境中的安全服役,设计了一种低磷镍/中磷镍/高磷镍的组合梯度化学镀镍磷层。采用SEM和XRD表征镀层的微观形貌和相结构,并通过电化学方法评价了镀层的耐蚀性。结果表明：相比于2A11铝合金基体,化学镀镍磷层的自腐蚀电位更正,自腐蚀电流更低;组合梯度镀层试样在35℃,5%NaCl盐雾环境中腐蚀500 h后,表面未见明显腐蚀现象,能满足航空铝合金耐腐蚀性能的要求。     

化学镀镍磷合金的动力学研究

在考察乳酸体系化学镀镍磷合金各反应物浓度、镀液的pH值和温度等因素对沉积速度影响的基础上,根据原子氢理论和实验规律,分析化学镀镍磷合金的反应过程,进行反应动力学研究,分别确定上述各因素所对应的反应动力学参数,提出化学镀镍磷合金的反应速度方程.由实验得出化学镀温度与反应速度的关系,通过该反应速度方程可预测出在乳酸体系镀液中的镀层沉积速度.     

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。     

铝及铝合金的电镀工艺综述

铝及铝合金具有密度小、较高的机械强度和较高的延展性、易加工的性能,因此在军工生产和民品生产中得到广泛应用。介绍了铝及铝合金５种镀前处理方法以及６种电镀工艺,为铝及铝合金电镀生产和发展起到了一定的借鉴作用。     

A new method for electroless Ni-P plating on AZ31 magnesium alloy

Coating Ni-P films on AZ31 magnesium alloys via electroless plating and organic coatings (organsilicon heat-resisting varnish), was studied. An organic coating was proposed as the interlayer between Ni-P coating and AZ31magnesium alloy substrate, to replace the traditional chromium oxide plus HF pretreatment. The Ni-P deposited on the interlayer was also characterized by its structure, morphology and corrosion-resistance. The interlayer 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. The result of the cross-cut test indicates the adhesion between the substrate and the interlayer is good enough. A Ni-P film with fine and dense structure was obtained on the AZ31 magnesium alloy. The electrochemical measurements show that the sample with Ni-P film exhibits lower corrosion current density and more positive corrosion potential than the substrate. Furthermore, the Ni-P coating on the AZ31 magnesium alloy exhibits high corrosion resistance in the rapid corrosion test illustrated in this paper. The method proposed in this work is environmentally friendly: no fluoride or hexacalent chromium compounds are used. In addition, it provides a new concept for plating the metals, which are considered difficult to plate due to high reactivity.     

The effect of SiC particles added in electroless Ni-P plating solution on the properties of composite coatings

To verify the relationship between the properties of composite coatings prepared on Q235 steel and the SiC content of electroless Ni-P-SiC composite coatings, systematic experiments with varied SiC contents and surfactants have been conducted. The experimental results indicated the approximate linear relation between the SiC content and the hardness of composite coatings. With the increasing of SiC content, wear resistance increases correspondingly. In particular, the effect of SiC content on the corrosion resistance of Ni-P-SiC composite coatings immersed in different corrosive solutions (i.e. 5% H₂SO₄, 20% NaOH and 3.5% NaCl) is explored, followed by a comparative analysis of the corrosion resistance between Ni-P and Ni-P-SiC coatings. Corrosion test indicates that NaOH solution makes no differences in the corrosion resistance between Ni-P coatings and electroless Ni-P-SiC composite coatings, both being uncorroded. Exposed to NaCl solution, the corrosion resistance of electroless Ni-P-SiC composite coatings decreases gradually with the increasing of SiC content in coatings. In H₂SO₄ solution, the corrosion resistance of coatings increases initially and decreases afterwards with the sustained increasing of SiC content in coatings, and the optimized corrosion resistance is obtained at a SiC content of 9.41 wt.%. Finally, a competent electroless Ni-P-SiC composite plating process producing a high wear resistance and sound corrosion resistance of the coatings is obtained.     

Improved microhardness and wear resistance of the as-deposited electroless Ni-P coating

The coatings with different phosphorus contents were obtained by varying the ratio of lactic acid to acetic acid in the electroless plating bath. With the increase of phosphorus content, the structure of the electroless Ni-P coating transformed from nanocrystalline to a mixture of nanocrystalline and amorphous phases, then to amorphous phase. A record high hardness value of 910 HV_0.1 of as-deposited Ni-P coating was obtained at 7.97 at.% phosphorus content, and high wear resistance was accordingly achieved. The refined nanocrystalline grains with an average size of ~ 4 nm were found to be responsible for the record high hardness and improved wear resistance of the as-deposited Ni-P coating.     

Direct electroless Ni-P plating on AZ91D magnesium alloy

An electroless Ni-P plating treatment was applied on AZ91D magnesium alloy to improve its corrosion resistance. Optimum pretreatment conditions and optimum bath of electroless nickel plating for magnesium alloy were found through many experiments. In order to avoid bother of pre-plating medium layer, a set of procedure of direct electroless Ni-P under the acid condition was investigated. The properties of the coating with 10% phosphorus were investigated. The results show that a coating with high hardness, low porosity and good adhesive strength is obtained. X-ray diffraction patterns show that the structure of the coating is an amorphous phase. After annealing at 400 ℃, the amorphous phase of Ni-P is transformed to crystalline phases, and some intermetallics as Ni3P and Ni5P2 are deposited from Ni -P solid solution along with an enhancing hardness from Hv 450 to Hv 910.     

Corrosion and wear properties of electroless Ni-P plating layer on AZ91D magnesium alloy

A direct electroless Ni-P plating treatment was applied to AZ91D magnesium alloy for improving its corrosion resistance and wear resistance. Corrosion resistance of the Ni-P coatings was evaluated by potentiodynamic polarization and immersing experiments in 3.5% NaCl solution. The wear resistance of the coatings was investigated by the wear track and the mass change after ball-on-disk experiment. The results show that corrosion resistance and wear resistance of the AZ91D alloy are greatly improved after direct electroless Ni-P plating. No discoloration is noticed until 4 d of immersion in 3.5% NaC1 solution. Potentiodynamic polarization experiments show that the free corrosion potential of magnesium alloy is shifted from -1 500 mV to -250 mV and passivation occurs at 1 350 mV after direct electroless plating. The friction coefficients and wear rates of Ni-P coating and Ni-P coating after tempering are 0.10-0.351, 9.038×10^-3 mm^3/m and 0.13-0.177, 3.056×10^-4 mm^3/m, respectively, at a load of 1.5 N with dry sliding. Although minor hurt on corrosion resistance was caused, significant improvement of wear resistance was obtained after tempering treatment of the coating.     

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.     

中温酸性化学镀Ni-P合金耐蚀性能研究

为提高化学镀Ni-P合金耐蚀性能,以Q235钢为待镀基体,在中温的酸性条件下,采用正交试验方法得到镀层耐蚀性最佳的工艺条件为:镀液pH值 5.2;Ni2 与H2PO2-的摩尔比为0.48;复合络合剂乳酸15mL/L 丙酸5mL/L;加速剂NaF 0.4g/L;热处理温度500 ℃.在此条件下,腐蚀电流为2.166×10-5A,可较好地提高镀层耐蚀性.