金属腐蚀给社会发展带来巨大的经济损失与危害,随着工业与科学技术的发展,腐蚀科学在国民经济中所占地位越来越重要。
化学镀非晶态Ni-P合金镀层具有独特的物理、化学和机械性能,尤其是优良的耐蚀性、耐磨性、顺磁性和析氢活性,在各行各业中得到广泛的应用。
然而由于化学镀镍磷合金沉积过程是按梗球无规则密堆积模型进行的,镀层中难免会有孔隙。
镀层孔蚀是限制镍磷镀层在海洋环境中广泛应用的主要原因。
因此,如何有效地增强化学镀镍磷合金的耐蚀性能已是当务之急。
本文首先研究了普通工业铁垫片单/双层镍磷合金的化学镀工艺,通过试验发现,在3.5wt% NaCl溶液中,实施双层化学镀镀层合金自腐蚀电位比单层的提高100mV以上,极化电阻明显变大,化学反应电荷转移电阻和钝化膜电阻也明显变大;海水全浸实验中,出现点蚀的时间比单层的延长了1～5h。
实验表明,双层化学镀工艺比单层化学镀工艺能更好的提高耐蚀性能。
化学镀层不可避免的存在着各种孔隙,当镀层厚度不高或者不能单靠增加镀层厚度来消除化学镀过程中的缺陷时,需要对镀层表面实施封孔处理。
本文采用有机硅封孔剂对镀层合金进行封孔处理,由于封孔剂能够很好地渗入孔隙并与镀层及基体交联,达到封闭镀层孔隙的目的,从而增强镀层的耐蚀性能。
通过实验发现,封孔后的镀层自腐蚀电位明显提高,在腐蚀环境中出现点蚀的时间明显延长,极化电阻明显变大,电化学反应电阻和表面膜电阻也明显变大,实验结果表明封孔工艺能增强镀层耐蚀性能。
同时,封孔温度对封孔效果产生明显影响,电化学实验与海水全浸实验结果表明,不同温度封孔均能够提高镀层的耐蚀性能,在50℃时封孔达到最佳效果。
化学镀层在初次封孔后耐蚀性能提高的仍不理想,或者初次封孔后表面缺陷仍未消除,就需要对镀层实施二次封孔处理。
本文在有机硅初次封孔后用丙烯酸树脂对化学镀双层镍磷实施二次封孔处理,丙烯酸酯聚合物具有优良的成膜性与粘接性等优质特性,能很好的起到再次封孔的作用,从而再次提高镀层的耐蚀性能。
通过实验发现,二次封孔处理后的镀层在海水全浸时腐蚀出现的时间明显延长,极化电阻显著变大,阻抗谱图中电荷转移电阻、表面膜电阻、孔内电阻值也显著变大。
通过试验结果解释了二次封孔对耐蚀性能的影响,表明二次封孔能够显著提高镀层的耐蚀性能。
同时,二次封孔液的组成对二次封孔效果产生明显影响,实验结果表明不同组成的二次封孔工艺均能显著提高镀层的耐蚀性能,在质量组成为树脂:二甲苯=3:7时二次封孔达到最佳效果。
Metal corrosion causes great economic loss and damage to industry and society. With the progress of industry and technology, anti-corrosion holds more and more important position in the national economy. Due to the unique physical, chemical and mechanical characteristics of Ni-P deposits, such as the anticorrosive property, wear resistance, paramagnetic characteristic, high hardness and the electro-catalytic activity of hydrogen evolution, the Ni-P deposits had been used widely in various fields. But the particles of the Ni-P deposits were unregulated. So it was hard to avoid the pinholes in the deposits especially in brine mediums. Pit corrosion was the main reason why the electroless Ni-P deposits were limited to be used widely. So how to effectively enhance the corrosion resistance of the electroless Ni-P deposits was the urgent affair.This article initially researched the process of single / double nickel-phosphorus electroless deposit(s) on common industry iron mat slices. Through the test it was found that,in 3.5wt% NaCl solution, the corrosion potential of the double Ni-P electroless deposits was higher more than 100mV than the single electroless deposit, the polarization resistance was significantly larger, and the charge transfer resistance and the passivation film resistance also became larger. And in the test on the plates plunging in the sea water completely,the time of the appearance of pitting was longer 1～5h than the latter. Experiment results showed that the double electroless deposits enhanced the corrosion resistance better than the single electroless deposit.Electroless deposits have porosity inevitably. When the thickness of electroless deposits isn’t high, or the disfigurements aren’t eliminated just by increasing the thickness of electroless deposits, the surface of electroless deposits needs to be sealing-treated. Silicone was used for sealing-treatment to electroless deposits in this article. Because the sealing agent could penetrate into the pinholes of the deposit and had good crosslink with the deposit, the number of the pinholes on the corroded deposit decreased after sealing-treatment, thus corrosion resistance is increased. Through experiments it was found that after sealing-treatment, the corrosion potential improved significantly, the time of the appearance of pitting in the corrosive environment was extend significantly, the polarization resistance was significantly larger, and the charge transfer resistance and surface film resistance alsobecame larger. Experiment results showed that the corrosion resistance could be enhanced through the sealing-treatment. At the same time, temperature made a great impact on sealing effect. Electrochemical experiments and the test on the plates plunging in the sea water completely showed that sealing-treatment could improve corrosion resistance of deposits at different temperature and up to the best effect at 50℃.If the improvement of corrosion resistance of electroless deposits is far from ideal after first sealing-treatment, or the disfigurements aren’t eliminated after first sealing-treatment, electroless deposits need to be second sealing-treated. In this article, acrylic resin was used for second sealing-treatment to double electroless Ni-P deposits after first sealing-treatment by silicone. Acrylic ester polymers have good characters such as good filming character and adhesive ability and so on, so it has the function of sealing the pores again and can improve corrosion resistance of deposits. Through experiments it was found that after second sealing-treatment the time of the appearance of pitting in the corrosive environment extended significantly, the polarization resistance was significantly larger, and the charge transfer resistance, surface film resistance and hole resistance in impedance spectra also became larger. The impact of second sealing-treatment on corrosion resistance was explained through the results, and it showed that second sealing-treatment could improve corrosion resistance of deposits. At the same time, quality proportion of second sealing-treatment liquid made a great impact on second sealing effect. Experiment results showed that second sealing-treatment could improve corrosion resistance of deposits at different quality proportion and up to the best effect at acrylic resin:xylene=3:7. 更多中温低磷化学镀镍磷合金工艺研究Mid-temperature and Low-phosphorus Electroless Nickel PlatingTechnology∙分页下载∙分章下载∙整本下载∙在线阅读∙不支持迅雷等下载工具。