(Ni-W-P)-SiC复合镀层的脉冲电沉积及其耐蚀性

研究了(Ni—W—P)—SiC复合镀层的脉冲电沉积工艺及耐蚀性。结果表明：(Ni—W—P)—SiC复合镀层的脉冲电沉积速率比直流电沉积大,脉冲镀层的耐蚀性优于直流镀层和1Cr18Ni9Ti不锈钢;脉冲频率和占空比对镀层的沉积速率、镀层成分以及镀层的耐蚀性都有较大的影响。     

脉冲电镀镍及其性能的研究

采用瓦特镀镍液,研究了脉冲占空比、平均电流密度、温度对电沉积速率,镀层光亮度和镀层在w=3.5%的NaCl溶液中耐蚀性的影响.用扫描电镜研究了直流和脉冲镍镀层的表面形貌.结果表明:电沉积速率随脉冲占空比、平均电流密度及温度的增大而加快;镀层耐蚀性,光亮度随脉冲占空比增大而变差,随温度、平均电流密度的增大先变好后变差.较佳脉冲电镀条件为:平均电流密度0.75 A/dm~2,脉冲占空比5%,温度45～50 ℃,pH 2.5～3.0.X射线衍射分析结果表明,与直流镀镍相比,脉冲镍镀层在(111)晶面存在择优取向,镀层更致密,性能更好.     

电沉积方式对镍-锡-锰合金镀层耐蚀性的影响

采用直流(DC)、脉冲(PC)和超声脉冲(UPC)电沉积方式在Q235钢表面制备Ni-Sn-Mn合金镀层,利用扫描电子显微镜(SEM)、辉光放电光谱仪(GDS)、X射线衍射仪(XRD)、Tafel曲线和电化学阻抗谱(EIS)研究了不同电沉积方式对镀层表面形貌、元素含量、沉积速率、相结构和耐蚀性的影响。结果表明,分别采用直流、脉冲、超声脉冲电沉积方式制备的镀层,Ni和Sn质量分数依次减小,Mn质量分数依次增大,沉积速率依次提高;直流电沉积镀层晶粒粗大,存在裂纹和孔隙,耐蚀性较差;脉冲电沉积镀层晶粒细化,无明显缺陷,耐蚀性较高;超声脉冲电沉积镀层均匀致密,呈非晶结构,在3.5%Na Cl溶液中具有最正的自腐蚀电位(-0.346 V)、最低的自腐蚀电流密度(3.162×10~(-8)A/cm~2)和最大的电荷转移电阻(9 143Ω·cm~2),镀层耐蚀性最好。     

电沉积纳米晶镍-铁-铬合金

采用直流和脉冲电沉积方式从三价铬的氯化物镀液中沉积出镍-铁-铬纳米合金镀层，利用扫描电镜分析镀层形貌及晶粒尺寸，研究了沉积速率，电流效率，三价铬浓度及pH值随沉积时间的变化关系，结果表明，脉冲电沉积所得镀层的结构和性能均优于直流电沉积，这是由于脉冲电沉积存在断电时间，使得电极表面扩散层中金属离子的浓度得到及时恢复。     

脉冲电沉积纳米镍-碳化硅复合镀层的性能

分别采用直流(DC)和换向脉冲电流(PRC)电沉积法制得纳米Ni-SiC复合镀层。采用X射线衍射仪、扫描电镜、能谱仪对比研究了纯Ni镀层和Ni-SiC复合镀层的微观结构、宏观残余应力、表面形貌及成分。用浸泡法研究了不同镀层在3.5%(质量分数)NaCl和10%(体积分数)H2SO4溶液中的腐蚀行为。结果表明,脉冲电沉积能改变镀层的微观结构,有效提高镀层硬度,降低宏观残余应力。脉冲电沉积所得到的纯Ni镀层和纳米Ni-SiC复合镀层在3.5%NaCl及10%H2SO4溶液中的耐蚀性均优于直流镀层。脉冲镀层在3.5%NaCl溶液中受腐蚀很轻,主要腐蚀形态为点蚀,而在10%H2SO4溶液中,SiC粒子作为增强相使镀层的耐腐蚀性进一步提高。     

脉冲电沉积RE-Ni-W-B复合镀层的研究

研究了脉冲频率和占空比对电沉积RE-Ni-W-B复合镀层硬度及沉积速率的影响,以及热处理温度对复合镀层硬度、磨损率及抗高温氧化性的影响.结果表明,当脉冲频率(f)和占空比(r)控制在1000 Hz和3∶1时,复合镀层硬度最高,厚度最大,分别为636 HV和0.0281 mm.使用脉冲电流,并在镀液中添加稀土元素,能有效降低镀层中镍含量,提高钨含量,降低复合镀层表面的裂痕.脉冲电沉积复合镀层的硬度均高于直流电镀复合镀层,磨损率均低于直流镀层.当热处理温度低于400°C时,热处理温度升高,复合镀层硬度增加,在400°C时,硬度最高,磨损率最低;高于400°C后,两种复合镀层的硬度又开始下降,磨损率上升.直流及脉冲复合镀层在600°C以下氧化增重都较小,600°C以后氧化增重明显增加.     

Q235钢表面电镀镍及其性能的研究

在Q 235钢表面电镀镍,以提高低碳钢表面的耐蚀性和可焊接性。对碱洗、酸洗、活化等前处理工艺进行了研究,着重研究了直流电镀和脉冲电镀的工艺参数和镀镍层的性能。结果表明:直流镀镍层和脉冲镀镍层都较为均匀、致密、无明显缺陷,且脉冲镀镍层比直流镀镍层结构更加紧密;加搅拌后所得镀层的实验结果明显优于不加搅拌时所得镀层的;脉冲镀镍层的自腐蚀电位明显高于直流镀镍层的,且加搅拌后,自腐蚀电位进一步提高。     

脉冲电沉积镍及其合金的研究现状与展望

回顾了近几年来脉冲电沉积在镀镍及Ni-P、Ni-Fe、Ni-Zn、Ni-Co及Ni-Cu等镍合金镀层的应用研究现状,对直流电沉积和脉冲电沉积所得镀层的硬度、耐磨性、耐蚀性、孔隙率及镀层的晶粒尺寸等进行了比较,并对脉冲电沉积今后的发展前景作了展望.     

复合电沉积Ni-W-P-CeO_2-Al_2O_3镀层耐蚀性能的研究

采用复合脉冲电沉积法制备Ni-W-P-CeO2-Al2O3复合镀层,研究了该镀层耐蚀性能。实验结果表明：镀层的耐蚀性随着制备温度的升高而明显得到提高,同时随着电流密度的增大,镀层的腐蚀速率降低,耐蚀性能得到提高,升高到一定的程度后,耐蚀性反而降低。随着电沉积时间的延长,镀层的耐蚀性能明显提高,但时间延长到一定程度后,耐蚀性变化不明显。经热处理后,Ni-W-P-CeO2-Al2O3复合镀层耐蚀性均有所提高。     

加速剂对镍镀层耐蚀性的影响

研究了NaF和KIO3对Q235钢表面电沉积Ni-P合金层沉积速率的影响,并通过浸泡实验考察了Ni-P合金镀层在质量分数分别为3.5%的NaCl,10%的NaOH和5%的HCl等三种溶液中的耐蚀性.结果表明:NaF并没有提高镀层的沉积速率,而加入KIO3则提高了镀层的沉积速率.同时,加入NaF或KIO3后均能明显改善Ni-P合金镀层的耐蚀性.     

The effects of pulse plating variables on morphology and corrosion behavior of Zn–Fe alloy coatings

Considerable researches have been focused on zinc–iron (Zn–Fe) alloy coatings due to their superior characteristics among zinc alloy electrodeposits in recent years. The corrosion behavior of these coatings depends on the phase structure and morphology of the Zn–Fe deposits. In this work the effects of pulse plating variables such as current density, off-time, frequency and pulse modes on the morphology and phase structure of Zn–Fe deposits was studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometry (EDS) analysis. The corrosion behavior of these coatings was measured by means of polarization curves and Neutral salt spray tests. It was shown that pulse reverse coatings exhibit excellent resistance to corrosion in comparison with normal pulse and direct current conditions.     

Pulse current electrodeposition and corrosion properties of Ni–W alloy coatings

Ni–W alloy coatings were prepared on a mild steel substrate by means of pulse current (PC) and compared to the coatings electrodeposited by direct current (DC). In particular the study dealt with the influence of the frequency using pulse current on the surface morphology while maintaining a constant duty cycle. A constant charge for DC and PC electrodeposition of Ni–W alloy coatings was used. The morphology of the coatings was explored by scanning electron microscopy and the composition of the coatings was analysed by X-ray powder diffraction and energy dispersive X-ray analysis. Corrosion resistance of Ni–W alloy coatings was investigated by potentiodynamic polarization in a chloride medium. The corrosion products were analysed by Raman spectroscopy. It was found that the temperature of the electrolysis affects current efficiency of the DC and PC electrodeposition. The frequency of pulse electrodeposition alters the morphology of the Ni–W alloy coatings. There was evidence of the positive influence of increased tungstate concentration in the electrolyte on corrosion resistance of the Ni–W alloy coatings.     

脉冲无氰镀银及镀层抗变色性能的研究

采用赫尔槽试验筛选出一种阴离子表面活性剂及含氮杂环化合物作为脉;中无氰镀银的添加剂,并初步确定了无氰镀银的工艺条件及脉冲条件一通过正交试验进一步化化脉冲条件及镀银添加剂含量分别为：脉宽1ms、占空比10％、平均电流密度0．6A／dm^2、阴离子表面活性剂及含氮杂环化合物含量分别为12mg/L、110mg/L测定了该镀银层的耐蚀性、抗变色性能及与基体的结合力,并用扫描电镜对其微观形貌进行了观察。结果表明,脉冲无氰镀银层的抗变色性能优于直流无氰镀银层;光亮镍打底后再脉冲无氰镀银,可获得更加光亮、结晶细致的镀银层,且抗变色性能及耐蚀性均增强.     

A study on the electrocodeposition processes and properties of Ni�CSiC nanocomposite coatings

Ni–SiC nanocomposite coatings were prepared on a brass substrate by electrocodeposition. The electrodeposition was carried out by adding the SiC nanoparticles to a nickel-containing bath. Nickel deposition processes were analyzed by cathodic polarization curves, and the plating parameters were determined preliminarily by analyzing the effects of different technological parameters on the deposition process. Then, electrocodeposition processes were carried out with different concentrations of SiC nanoparticles in the bath. The effects of current density, stirring rate, and SiC nanoparticle’s concentration in the plating bath on the hardness of coatings were investigated by microhardness tests. Besides the microhardness tests, wearing tests and corrosion tests were also applied to the coatings with the highest hardness and coatings of pure nickel. The structures and surface morphologies of the coatings were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. The experimental results show that the microhardness of the codeposited coating increases with increasing current density and attains a maximum at the SiC concentration of 6 g/L. The decrease in the microhardness at higher SiC concentrations may be due to agglomeration of nanosized particles in the plating bath. Increasing the stirring speed did not give a better quality deposition as coatings produced at low stirring rates always had higher microhardness values than did those at high stirring rates. Furthermore, the Ni–SiC nanocomposite coatings have lower friction coefficient and better corrosion resistance than those of pure nickel coatings.     

双向脉冲电镀纳米级镍镀层耐腐蚀性能研究

用直流电沉积法制备了普通光亮镍镀层,同时用双向脉冲电镀制备了纳米级镍镀层。用X射线衍射(XRD)、扫描电镜(SEM)等方法研究了镀层的晶粒尺寸、组织结构和表面形貌,通过孔隙率测定、盐雾试验、静态浸泡腐蚀失重试验和电化学方法等测试了镀层的耐蚀性能。结果表明,采用双向脉冲电流制备的纳米级镍镀层的耐蚀性明显优于普通直流镍镀层。     

脉冲与直流电沉积RE-Ni-W-P-SiC复合镀层性能研究

采用脉冲与直流电沉积，研究了RE—Ni—W—P—SiC复合镀层的性能。结果表明：在相同的条件下，采用脉冲电流得到的复合镀层比直流电流得到的镀层有更高的硬度、沉积速度，同时耐磨、耐蚀性也得到提高。     

不同电源模式下微弧氧化制备陶瓷膜的性能对比研究

在硅酸钠、钨酸钠、硼酸、偏铝酸钠和乙二胺四乙酸二钠的复合电解液中,分别采用交流电源和脉冲电源,利用微弧氧化方法,在ZL102铸造铝合金上制备了陶瓷膜层。通过扫描电镜（SEM）观察,交流电源模式制备的陶瓷膜层表面孔洞少,比用脉冲电源制备的陶瓷膜形貌好。利用电化学方法分析了陶瓷层的防腐蚀性能,交流电源制备的陶瓷膜层耐腐蚀性能好。     

Evaluation of the corrosion resistance of phosphate coatings obtained by anodic electrochemical treatment

The corrosion resistance of phosphate coating obtained by anodic electrochemical treatment at 4–6 mA/cm² is addressed in this paper. The corrosion performance of these coatings is also compared with the coatings obtained by chemical treatment. The regenerated phosphoric acid under the influence of anodic current causes a large variation in morphological features of the coatings. Immersion and salt spray tests indicate the ability of these coatings to act as a barrier film on mild steel. Polarization and electrochemical impedance spectroscopic (EIS) studies indicate that the corrosion resistance of phosphate coatings obtained by anodic treatment decreases with increase in current density employed for deposition. In spite of their higher coating weight, the corrosion resistance of phosphate coatings obtained by anodic treatment is inferior to those obtained by chemical treatment. The porosity or discontinuities created due to the dissolution of the coating under the influence of anodic current are considered responsible for the inferior corrosion resistance of these coatings. The study concludes that anodic treatment has only a limited scope for preparing phosphate coatings with improved corrosion resistance.