铸铝合金镀银前浸锌工艺的研究

为解决铸铝合金镀银件镀层结合力的问题,研究了镀银前浸锌工艺中退锌时间对镀层结合力的影响。通过扫描电子显微镜观察了不同退锌时间下浸锌锌层的表面形貌,通过热震法对镀层结合力进行了测试和评价。结果表明,在退锌时间为15 s时,二次浸锌能得到均匀、致密、较薄的锌层,其镀层结合力最好。     

钛合金化学镀Ni-P合金前处理工艺的研究

研究了浸蚀、浸锌等前处理过程对钛基体渗氢及化学镀Ni-P合金镀层与基体结合力的影响。结果表明,采用混酸浸蚀液,可以有效除去钛合金表面的钝化膜,控制基体中的渗氢量;二次浸锌得到的Ni-P合金镀层结合力较好,镀层均匀、紧密,镍晶粒尺寸较小。     

活化工艺对铝合金化学镀镍的影响

通过开路电位测量分析了浸锌、钯活化、银活化和增强银活化对铝合金化学镀镍引发过程造成的差异.采用扫描电镜、能谱仪和结合力测试比较了上述4种活化方式对化学镀镍层表面形貌、元素组分和结合力的影响.结果表明,浸锌、钯活化、银活化和增强银活化引发铝合金化学镀镍的诱导时间分别约为50、5、10和2 s,钯活化和银活化的引发效率比浸锌高,所有活化方法下制得的镍镀层都有良好的结合力.采用增强银活化时镍镀层的表面形貌最佳.     

高硅铸铝合金镀前浸锌液

针对高硅铸铝件在组成，组织与性能上的特点，研究了8种高硅铝合金镀前浸锌液。用扫描电镜（SEM）观察了8种不同的浸锌液配方浸锌的试片的表面浸锌膜的微观形貌，测定了浸锌后镀镍层与试片的结合力，优选了能获得良好结合力的最佳浸锌液配方。并研究了随浸锌时间的增加，锌晶核的析出与成长的过程，结果表明，当氢氧化钠140g/L，氧化锌14～20g/L、氯化镍1.5g/L时，试片镀镍后结合力良好。发现浸锌液能够溶解铝合金部分组织，并在铝表面造成孔洞，这种孔洞对镀层起着锚链作用，铝合金表面孔洞的均匀分散以及细小锌晶粒的高度弥散是得到良好结合力的前提。     

镀液成分对纳米镍-钴合金镀层显微硬度的影响

研究了镀液成分(糖精和钴)对脉冲电沉积纳米镍-钴合金镀层显微结构和显微硬度的影响.结果发现:镀液中糖精和钴的加入都可以细化晶粒,提高硬度;同时其质量浓度的进一步增加又都可以使镀层硬度下降.通过镀液中钴的加入,有机晶粒细化剂(糖精)的用量可以明显减小,这将有助于镀层性能的提高.由于糖精的过量使用会使镀层中硫和碳的杂质量增加,而这些杂质往往存在于晶界上,使镀层韧性下降.     

稀土添加剂镀镍耐蚀性能的研究

稀土元素在金属表面处理中已得到了广泛的应用。稀土在镀镍工艺中,能使镍镀层变成结构致密的稀土镍合金镀层,从而命名镍镀层的结晶细化,耐蚀性能大大提高,稀土镍 基合金用于海轮的累旋桨,能使耐蚀性能提高10倍。稀土能使镍铁合金镀层结晶细化,结构致密,提高镀层的耐蚀性能。 Ni-P合金镀液中加入稀土后能使镀层中的镍 颗粒分布均匀、结合力好、磨损量减少,且镀层表面均匀、光亮。笔者通过长期的研究发现,在镀镍液中加入的稀土和其它配伍物混合制得的添加剂后,能明显优化镀镍的工艺条件,提高镀镍层的耐蚀能力。     

浸锌条件对铝合金浸锌层显微组织的影响

利用扫描电镜研究了浸锌条件对铝合金浸锌层微观形貌的影响,结果表明,随浸锌时间的增加,锌晶粒不断成核并生长,晶粒尺寸及致密度逐渐增加,晶粒之间彼此相互联结,二次浸锌比一次浸锌所得锌晶粒细小、致密、均匀;随浸锌温度的升高,锌晶粒形状由粒状变为片状,并出现脱落,最适宜的浸锌温度为20～30℃;低浓度无氰多元浸锌溶液所得浸锌层优于传统浓浸锌溶液、稀浸锌溶液、稀浸锌-镍合金溶液;铝合金镀前预处理对浸锌层微观形貌影响也较大。     

二次浸锌预处理对钛合金化学镀镍沉积行为和镀层结合力的影响

通过电化学测试和扫描电镜分析,研究了钛合金在二次浸锌过程中的电位变化规律及锌层形成过程,并考察了二次浸锌对碱性化学镀镍初期沉积行为的影响,探讨了二次浸锌改善镀层结合力的基本原理。结果表明,钛合金在一次浸锌过程中经历了氧化膜溶解、薄锌层生长及锌层生长-溶解动态平衡三个阶段,表面形成了稀疏的晶须状锌层;二次浸锌的总体规律与一次浸锌类似,但锌层很快达到生长-溶解动态平衡,形成的锌层更均匀、致密,覆盖度更高。二次浸锌有利于后续化学镀镍快速形成完整、均匀的镀层,以及提高钛合金基体与镍镀层之间的结合力。     

新的铝合金表面化学镀镍磷合金前处理工艺及镀层性能研究(Ⅰ)

研究了一种新的含镍盐的高碱性表面活化液来替代常规的浸锌处理工艺。对镀层结合力测试表明,此种前处理工艺能获得同浸锌处理一样满意的结果。对用新的前处理工艺所得镀层性能,如硬度和耐蚀性等进行了研究。     

电化学辅助一步法浸锌工艺的初步研究

研制了一种一步法浸锌工艺.采用电化学辅助的方法改变铝在浸锌液中的界面电位并加速铝表面氧化膜的活化,以获得均匀致密的浸锌层.研究了电流密度、时间、温度、搅拌等工艺参数对3003铝合金上铜镀层结合力的影响.该浸锌液的工作温度为0～15 ℃.当控制通过试样的阳极电流密度为0.6～1.5 A/dm2,浸锌时间30～60 s时,在静止或搅拌的情况下都能获得结合力较佳的铜镀层.该方法无需硝酸浸蚀步骤,可一步完成铝及其合金的浸锌处理,有着良好的应用前景.     

Novel copper immersion coating on magnesium alloy AZ91D in an alkaline bath

Copper immersion coating of magnesium alloys has, to date, been conducted only in acidic baths. This article describes a novel alkaline bath for copper immersion coating on AZ91D magnesium alloy. Prior to the coating process, a chemical etching process of the magnesium substrate was optimized using orthogonal experimental methodology. The copper immersion coating was then investigated with regard to the effect of pH and fluoride content in the deposition bath. It was revealed during the coating process that an increase of pH and fluoride content led to a surface film formation on the magnesium substrate. The surface film formation occurred simultaneously with copper reduction, rendering a controlled magnesium dissolution, thereby a controlled copper deposition. With optimized conditions of chemical etching and immersion coating processes, uniform copper deposits were achieved.     

预处理对AZ91D镁合金化学镀镍的影响

以磷酸盐-氟盐-高锰酸盐配制镁合金的活化溶液,实现了镁合金表面直接沉积镍-磷合金镀层。采用扫描电子显微镜、能谱仪和X-射线衍射仪研究了镁合金活化后的形貌和成分。结果表明,活化转化膜层致密,主要成分为MgF_2-Mg_3(PO_4)_2复合结构。极化曲线和结合力测试表明,转化膜可有效地防止镀液对镁基体的腐蚀,所得镍-磷合金镀层致密,具有良好耐蚀性能,且镀层和镁基体间的结合力良好。     

氧化镍薄膜电致变色特性及机理研究

利用溶胶-凝胶浸镀法选择了合适的溶制和助剂及加料方式制得了稳定性高的溶胶,然后在ITO导电玻璃表面进行镀膜,通过对薄膜循环伏安曲线、透射率及X光电子能谱(XPS)的测定,分析了氧化镍薄膜的电致变色范围及薄膜的热处理条件,提出了氧化镍薄膜电致变色的机理。     

工艺参数对印刷线路板表面化学镀镍/置换镀金层性能的影响

分析了工艺参数(如温度、pH值、沉积时间等)的变化时印刷线路板(PCB)表面化学镀镍/置换镀金层性能的影响。结果表明:工艺参数对镀层性能具有较大影响。在此基础上优化了化学镀镍/置换镀金工艺,获得了性能良好的镍/金镀层。     

Corrosion behaviour of electrogalvanized steel in sodium chloride and ammonium sulphate solutions; a study by E.I.S.

Zinc and zinc-nickel (13% Ni) electrodeposits were passivated by dipping in chromate baths and characterized by scanning electron microscopy. The corrosion behaviour was studied using a.c. electrochemical techniques; electrochemical impedance spectroscopy (EIS) measurements were performed at open circuit and under galvanostatic control during the 24 h immersion time. In sodium chloride solution the zinc-nickel electrodeposits show a better corrosion resistance compared to the pure zinc coatings. During the immersion time, a surface nickel enrichment was observed which, together with the zinc corrosion products, acts as a barrier layer reducing the total corrosion rate. In the same solution the passivation treatment improves the corrosion resistance of the electrodeposits; nevertheless, on zinc substrates, the protection exerted by the chromate film is not, always effective during the immersion time. On the contrary the chromate coating on zinc-nickel substrates induces a remarkable and durable improvement of the corrosion resistance reducing the zinc dissolution almost completely. In the ammonium sulphate solution, the corrosion mechanism is significantly influenced by hydrogen reduction on the zinc-nickel surfaces, and by the production of a local surface acidity which is aggressive for the chromate coatings.     

Optimization and performance analysis of copper immersion coating on AZ91 magnesium alloy

An orthogonal experimental methodology was used to study a copper immersion coating on AZ91 magnesium-alloy from a hydrofluoric acid-containing bath. Factors such as hydrofluoric acid concentration, sonication time, chemical etching, and activation process were considered in the design. The analysis of variance on the orthogonal experimental results was performed, resulting in an optimal condition for achieving a uniform copper coating with high coverage. Hydrofluoric acid was found to be an essential component in the copper immersion coating bath and a possible mechanism was suggested to explain its significance in terms of magnesium film destruction and magnesium dissolution.     

醋酸镍对AZ 63B镁合金微弧氧化膜耐蚀性的影响

在硅酸盐体系电解液中添加适量的醋酸镍及配位剂后,对AZ 63B镁合金进行微弧氧化处理,在AZ 63B镁合金表面制备了微弧氧化膜。研究了醋酸镍对微弧氧化膜耐蚀性的影响。结果表明:在电解液中添加醋酸镍,经微弧氧化后,镁合金表面生成了含Ni化合物的咖啡色氧化膜,耐蚀性得以提高。     

Corrosion behaviors of Zn/Al-Mn alloy composite coatings deposited on magnesium alloy AZ31B (Mg-Al-Zn)

After being pre-plated a zinc layer, an amorphous Al-Mn alloy coating was applied onto the surface of AZ31B magnesium alloy with a bath of molten salts. Then the corrosion performance of the coated magnesium alloy was examined in 3.5% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the single Zn layer was active in the test solution with a high corrosion rate while the Al-Mn alloy coating could effectively protect AZ31B magnesium alloy from corrosion in the solution. The high corrosion resistance of Al-Mn alloy coating was ascribed to an intact and stable passive film formed on the coating. The performances of the passive film on Al-Mn alloy were further investigated by Mott-Schottky curve and X-ray photoelectron spectroscopy (XPS) analysis. It was confirmed that the passive film exhibited n-type semiconducting behavior in 3.5% NaCl solution with a carrier density two orders of magnitude less than that formed on pure aluminum electrode. The XPS analysis indicated that the passive film was mainly composed of AlO(OH) after immersion for long time and the content of Mn was negligible in the outer part of the passive film. Based on the EIS measurement, electronic structure and composition analysis of the passive film, a double-layer structure, with a compact inner oxide and a porous outer layer, of the film was proposed for understanding the corrosion process of passive film, with which the experimental observations might be satisfactorily interpreted.     

镁合金化学镀镍工艺的研究

采用硫酸镍为主盐、次磷酸钠为还原剂,并在镀液中加入氟化物和稳定剂,研究了镁合金的化学镀镍工艺.运用正交试验分析了镀液中各主要组分对镀速及耐蚀性等影响,优选化学镀最佳工艺.该工艺沉积速率快,镀层耐蚀性优异.运用X-射线衍射方法对镀层的组织结构进行了分析,结果表明,镁合金化学镀镍层由非晶态的镍及部分微晶的镍组成.     

AZ91D镁合金化学镀镍前处理工艺研究

对AZ 91D镁合金碱性化学镀镍的前处理工艺进行研究,得到了镁合金一步磷化的前处理工艺,确定了AZ 91D镁合金磷化液的组成及工艺条件,经一步磷化前处理后即可进行化学镀镍.采用扫描电镜(SEM)、能谱成分分析(EDS)对磷化后的试片的微观形貌和组成成分进行了分析,并测定了AZ 91D镁合金及其化学镀镍后的Tafel曲线...