Influence of LaCl3 addition on microstructure and properties of nickel-electroplating coating

The influence of rare earth chloride LaCl3 ·7H2O addition on the microstructural features, phase structure, corrosion resistance and microhardness of nickel-electroplating was investigated. The Watts-type with different additive amounts of LaCl3·7H2O(0-1.2g/L) were used in the experiment. Surface morphologies of coatings were examined by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) was used to measure the coatings’ grain size and the microstructure of coatings was detected by X-ray diffraction (XRD). Corrosive investigation was carried out in 3.5 wt.% NaCl solution. The microhardness values of the coatings with different amounts of LaCl 3·7H2O were measured, and the mechanism of the variation in microhardness was studied. Results showed that the addition of rare earth lanthanum refined the grain size and improved the surface consistency of the coatings, meanwhile the microhardness and corrosion property of coatings were improved and achieved a maximum with arround 1.0g/L LaCl 3·7H2O addition in electrolyte. The preferred growth orientation of lanthanum doped coating was crystal face (200), meanwhile the La2 Ni7 phase was detected in the nickel coating by XRD and this was due to the induced co-deposition of elements La and Ni. The reason maybe was that the special out-layer electronic structure of element La raised the polarization of Ni cathode deposition, accelerated the nucleation of Ni and reduced hydrogen evolution from cathode surface.     

脉冲电镀Ni-SiC纳米复合镀层性能研究

以金属Ni为基质,通过脉冲电镀的方法将纳米固体微粒SiC掺杂进入镀层中,对复合镀层的结合力、耐磨性、耐蚀性、空隙率进行了分析与探索。     

有机杂环化合物对铝合金在3.5%NaCl介质中的缓蚀作用

添加有机缓蚀剂可以减缓或防止铝合金在3.5%NaCl溶液中的腐蚀。用失重法和电化学法分别研究了7种有机化合物对7075铝合金在3.5%NaCl溶液中的缓蚀行为,并用扫描电子显微镜(SEM)对铝合金样品在不同缓蚀介质中的腐蚀形貌进行了观测。失重法实验结果和Tafel极化测试结果均表明,这些有机化合物对铝合金有不同程度的缓蚀作用,其中7-氮杂吲哚的缓蚀效果最好,通过对铝合金样品表面孔蚀特征及电化学测量结果的分析,确定其缓蚀机理为阳极过程控制为主的成膜缓蚀剂。