电镀锌表面条纹缺陷成因分析

运用扫描电子显微镜和电子背散射衍射(EBSD)技术对电镀锌板表面暗条纹及冷轧基板对应缺陷进行了失效分析。结果表明电镀锌耐指纹板表面暗条纹缺陷形成有三种原因:1)钢板次表面的冶炼缺陷经后续轧制露头后引起后续电镀锌层异常,形成黑色条带缺陷;2)热轧基板表面点状夹杂物露头(或热轧轧辊剥落物、富Cr的氧化铁皮压入),周边区域酸洗不完全,形成锈蚀产物后在后续轧制工序被轧入表面,引起电镀锌层异常形成条纹缺陷;3)热轧时表面局部温度偏低,在二相区轧制形成的高斯织构遗传到冷轧板,电镀锌时形成丝状斑迹缺陷。     

电沉积纳米镀锌层的机理研究

对电镀锌进行纳米改性研究，得到层状纳米镀锌层。采用场发射电镜(FEG-TEM)观察镀锌层结晶的形态，X衍射分析镀锌层晶粒的尺寸，恒电位法和电化学交流阻抗方法研究了纳米镀锌层的电沉积机理。     

IF钢基板高速电镀锌的微观形貌和织构(英文)

采用高速电镀技术在无间隙原子钢(IF钢)基板上镀锌,借助扫描电镜和取向分布函数研究镀锌层的微观形貌和织构。结果表?镀锌层由一系列倾斜于基体表面紧密排列的六方形片晶组成,初始电沉积时基体表面氢氧化锌的大量吸附抑制锌的三维形核,二维晶核的外延生长以及IF钢基板的{111}纤维织构促进镀锌层{11.5}锥形非纤维织构的形成。镀锌层呈锥形织构时,片晶的滑移面与基体表面呈一定角度,保证镀层在受到轴向应力时产生一定量的分切应力,从而有利于自身的塑性变形。     

连续电镀锌-镍合金技术的研究

提出了连续电镀锌镍合金的高氯化氨-弱酸型镀液工艺参数,对镀液成分、pH值、温度、阴极电流密度对镀层镍含量的影响及连续电镀锌镍合金的镀速控制等问题进行了研究.得到外观良好、镍含量在13%～15%的锌镍合金镀层.     

大锌花热镀锌板表面亮点缺陷产生原因分析及对策

<正>生产有锌花热镀锌板时,一个锌花是由一个结晶中心长大而成,在单位面积上结晶中心越多则锌花越小,结晶中心越少则锌花越大。目前,有锌花热浸镀锌钢板广泛应用在建筑、装饰材料等领域。而亮点是纯锌镀层表面一种非常细微的缺陷,其产生原因主要有:镀锌基板表面缺陷,镀锌过程中清洗不良,炉内异物压     

热浸镀锌带钢表面条纹状缺陷产生原因分析

在生产热浸镀锌带钢时,带钢表面经常出现漏镀、黑点等各种缺陷,条纹状缺陷也是其中一种。采用扫描电镜和能谱仪对连续热浸镀锌带钢的镀层表面条纹状缺陷进行了测试与分析。研究表明,该条纹状缺陷位置处基板内存在裂缝,导致基板内表层出现了分层,裂缝内同时存在基板的氧化铁皮、氧化圆点和镀锌层,表面镀层较薄,该缺陷应为连铸板坯表面存在纵裂纹以及后续热轧轧制所致。镀锌板表面出现该缺陷后,不仅影响板面外观,而且在冲压成形过程中易发生镀层剥落和起皮而导致工件报废。     

780 MPa级热镀锌双相钢微观裂纹成因及改进措施

780MPa级热镀锌双相钢表面块状色差缺陷的原因为基板表面大量开口微观裂纹。微裂纹开口导致Fe2Al5抑制层形成异常,宏观表现为块状色差。微裂纹主要分布在带钢中部板面中间等热轧卷散热较慢位置,裂纹处珠光体晶粒较粗大。通过分析此带钢全流程氧化特性,带钢表层在加热炉中形成锚状氧化铁皮,附着在带钢基体上不易去除;在热轧工序中Si、Cr元素向表面富集形成硬质氧化圆点,附着在带钢近基体上。Si、Cr氧化圆点与粗大珠光体在冷轧过程中形成微裂纹。带钢在镀锌工序退火过程中,表面微裂纹在大张力作用下成为开口状态。微裂纹开口增加了基板与锌液接触面积,增加了锌液与铁的反应速度;同时裂纹开口导致带钢表面破碎,Fe2Al5抑制层无法良好结晶,这两点因素导致Fe_2Al_5抑制层无法良好形成。降低板坯加热炉温度,减少"锚状"氧化铁皮的生成。提高粗轧出口温度,形成疏松铁皮,在冷轧酸洗过程中带走Si、Cr氧化圆点。降低热轧卷取温度,使热卷带板中位置形成细小珠光体,提高开裂抗力。降低镀锌工序退火炉张力,减小微裂纹开口几率。通过以上措施,可有效改善780MPa级热镀锌双相钢表面微裂纹,消除色差。     

基板表层组织对Fe-16Mn-0.7C-1.5Al TWIP钢可镀性的影响

以16%Mn-0.7%C-1.5%Al (质量分数) TWIP钢为研究对象,采用热镀锌模拟实验研究了2种基板表层组织对TWIP钢可镀性的影响。使用180°折弯检测了镀层附着性,使用GD-OES分析了退火及镀锌试样表面的元素深度分布,使用SEM观察了试样表面和截面微观形貌。结果表明,通过预处理得到的TWIP钢表面一层铁素体晶粒可以有效改善TWIP钢的可镀性。当轧硬态的TWIP钢直接连续退火并热镀锌时,Mn元素形成了明显的外氧化,严重阻碍了镀液中的Al和基板反应形成Fe-Al抑制层,不仅漏镀明显,而且镀层附着性差。当使用经过预处理、表面有一层铁素体的TWIP钢进行热镀锌时,TWIP钢表面的细晶粒铁素体层有效抑制了退火过程中Mn元素外氧化,从而显著改善了锌液对带钢的润湿性,在镀层/基板界面位置形成了充分的Fe-Al抑制层。通过预处理得到的表面铁素体层可以有效解决16%Mn-0.7%C-1.5%Al TWIP钢的可镀性差和镀层附着性差问题。     

表面粗糙度对热浸镀锌镀层特征及耐蚀性的影响

为提升热浸镀锌钢板的表面质量,将热镀锌钢板进行连续热浸镀锌试验生产,采用场发射扫描电镜、显微镜和盐雾实验等手段,对生产试验的镀锌板进行相关的实验分析,研究了热浸镀锌基板表面粗糙度对含Sb和Pb的热浸镀镀锌板锌花尺寸均匀性和镀层厚度及物相组成特征的影响,以及锌花大小与耐腐蚀性的关系。结果表明:基板表面粗糙度越大,锌花尺寸越小且镀层厚度也小,δ相层中Fe元素含量较大,耐腐蚀性能较好。     

摩擦辅助喷射电沉积纳米晶镍的电化学腐蚀行为

采用摩擦辅助喷射电沉积工艺和传统喷射电沉积工艺制备纳米晶镍,用TEM对比分析了二者的组织结构,用电化学极化法研究了2种纳米晶镍层在3.5%NaCl(质量分数)溶液及1 mol/L H2SO4溶液中的腐蚀行为。结果表明,摩擦辅助喷射电沉积结晶过程更加均匀,制备的纳米晶镍层组织致密,晶粒细小,平均晶粒达到9.77 nm;在2种腐蚀溶液中,摩擦辅助喷射电沉积制备的纳米晶镍的电化学腐蚀性能均优于传统喷射电沉积;在NaCl溶液中,摩擦辅助喷射电沉积所制纳米晶镍在腐蚀过程中有钝化膜产生。并指出晶粒大小与微观缺陷是影响纳米晶镍耐腐蚀性能的2个重要因素     

2024铝合金浸锌工艺研究

试验研究了浸锌工艺及溶液组成对2024铝合金基体浸锌层及电镀镍层外观和结合力的影响,优化了浸锌液的组成及工艺条件.发现良好的浸锌层是提高镀层与基体结合力的关键.     

Probleme der Inhibitoren in der Galvanotechnik

Problems of inhibition in electroplating Inhibition in electroplating is understood to be a hindrance or perturbation of the electrocrystallization; these phenomena may, however, have a positive effect, too, and are often a necessary condition for obtaining coatings with particular properties. The inhibitors used are mostly connected with the incorporation of foreign matter in the coating. Inhibition is of particular importance with respect to the throwing and the levelling power, the type of deposit (e.g. glossy coatings) and various chemical and physical coating properties. The various metals are characterised by various sensitivities with respect to the inhibitor effect: nickel and other transition metals are highly sensitive, copper has medium sensitivity and zinc, cadmium and lead are little sensitive. Gloss formation is controlled in the case of nickel coatings by an inhibited crystallization which, in turn, is controlled by amorphous adsorption layers; it is characteristic in this context that the texture of the base material disappears already at low coating thicknesses, while it can be observed in the case of mat coatings even at considerable coating thicknesses.     

The Effect of NiAl Coatings on Oxidation Behavior of AISI 403 Stainless Steel

STAINLESS STEEL TYPE AISI403possess a highdegree of resistance to atmospheric corrosion becauseof its ability to form a dense adherent oxide film,whichprotects the material from further attack[1].Thiscomposition was developed to meet the requirementsfor some gas turbine components.The alloy is notparticularly recommended for use in hot corrosion andoxidation environments.Therefore,a protective coatinglayer is essential for such applications as hot sectioncomponents in gas turbine[2].A…     

化学镀镍作为钢酸性镀铜前处理工艺的应用研究

为了防止钢表面酸性电镀铜出现置换铜,采取在电镀铜前增加化学镀镍工序,研究了化学镀镍工艺对酸性电镀铜的影响。结果表明,化学镀镍时间超过6 min时(镍层厚度>2.5～3μm),工件在酸性镀铜液中浸泡10 min,无置换铜出现。化学镀镍层对后续的酸性镀铜层的表面形貌和附着力均无明显影响,表明化学镀镍可作为钢酸性镀铜的底层。     

Porosity of Electroless Nickel Coatings Investigated Using Different Porosity Tests and Their Application

The porosity of electroless nickel coatings on mild steel substrates having different substrate surface roughness and coating thickness was investigated using NSS (Neutral Salt Spray), ferroxyl, and SO₂ tests. In addition the influence of substrate surface roughness and coating thickness upon the properties of electroless nickel coatings was studied.

It was found that all porosity tests showed the same tendency for the porosity of electroless nickel coatings to decrease with decreasing substrate surface roughness and increasing coating thickness. The use of the SO² and ferroxyl test have the advantage over the NSS test as a routine quality control procedure in that they are both quicker to carry out and easier to interpret. A relationship between porosity, substrate surface roughness and coating thickness was established which might be used as an industrial quality control tool.     

Microstructure and properties of nanocrystalline nickel coatings prepared by pulse jet electrodeposition

The fabrication of nanocrystalline nickel coatings was conducted by pulse jet electrodeposition on the substrate of 45# carbon steel. The effects of average current density on the surface morphology, microstructure, average grain size and microhardness of nickel coatings were investigated by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and microhardness measurement. In addition, the corrosion resistances of coating and substrate were compared. It is revealed that the nickel coatings prepared by pulse jet electrodeposition exhibit a fine-grained structure with a smooth surface and a high density, although some pores and defects are still present in coatings. With the increase of average current density, the average grain size of nickel coatings is reduced at first and then increased. The coating with the optimum compactness, the smallest average grain size (13.7 nm) and the highest microhardness are obtained at current density of 39.8 A/dm2. The corrosion resistance is obviously increased for the coatings prepared by pulse jet electrodeposition; however, the corrosion rate is increased after a certain period due to the penetration of the corrosive media.     

Effects of Diffusion from Brass Substrates into Electrodeposited Tin Coatings on Corrosion Resistance and Whisker Growth

Tin coatings electrodeposited direct on brass have an initial trace zinc content which makes them liable to tarnish in atmospheres containing sulphur dioxide. When more zinc reaches the surface by diffusion from the substrate, susceptibility to corrosive agents increases. Undercoats of copper or nickel are effective long-lasting barriers to zinc diffusion but permit the slower and less damaging growth of intermetallic compounds. Increased thickness of tin coating delays the arrival of diffusing metal at the surface and also reduces the effect on solderability of corrosion of a diffused coating. Diffusion is faster in tin coatings deposited bright. Tests to assess the extent of zinc diffusion and the liability of a coating to deteriorate in long storage with corrosion risk are discussed. Susceptibility of tin coatings to whisker growth has some parallel with their tendency to interdiffuse with the substrate.     

The Structure and Protective Properties of Zinc and Nickel Alternate Electrodeposits

A NEW TYPE of coatings consisting of a large numberof laminar deposits has been the keen subject of muchresearch,because these layered-structure coatingspossess improved properties or novel phenomenon suchas increased mechanical strength,micro-hardness,giantmagnetoresistance and corrosion resistance[1"6'.Thesecoating systems with individual layers making upoverall structure are also called compositionallymodulated multilayer(CMM)coatings'3"5'.In view ofthe plating historical use of surface…     

Characteristics of Diffusion Annealing Between Martensitic Stainless Steel and Nickel in the Form of Coating and Foil

Characteristics of interaction between martensitic stainless steel type AISI 410 with nickel in the form of coating layer and foil were investigated. Nickel was coated on AISI 410 substrate by electroplating in various thicknesses (6-16 μm). The 300-μm-nickel with purity of 99.9% was employed as a foil layer. All specimens were annealed in the temperature range of 700-900 °C for 5, 10, 15, and 60 min. Optical microscopy, SEM and EPMA analyzer were carried out in order to characterize the interdiffusion behavior differences between nickel and AISI 410 while using nickel layer in different form. It was observed that the thickness of nickel coating had a minor effect during annealing on the interaction between Ni and substrate at faying surface. However, the results show that the interaction of nickel coating layer with base material is much faster than foil layer during annealing process. This study suggests that the coating layer diffused faster to the substrate than foil layer; moreover, in the former case, heavy outer load was omitted. The concentration profiles were plotted for two cases. Although in case of using layer in the form of coating the annealing time was relatively short (5-15 min), it was observed that the concentration profiles for main elements had shapes close to the theoretical curve. For various thicknesses (6-16 μm) of Ni coating, the experimental results show that the interaction at faying surface caused the thickness of nickel coating growth. The diffusion zone width was plotted against the annealing temperature and time for both cases and the growth of the diffusion zones was compared.     

电镀Zn-In合金在碱性溶液中的电化学行为

用电沉积的方法在Ni基体上制得了Zn-In合金,采用ICP,SEM和EDS研究了电镀Zn-In合金的组织和成分,采用LSV,CV和EIS等方法研究了不同镀时下电镀Zn-In合金在碱性溶液中的电化学行为.结果表明,沉积时间越长,合金中In的含量越高;与镀时为20和30 min相比,10 min为较佳镀时,在此镀时下,Ni基体表面能形成均匀平整的Zn-In合金,延长镀时,会因为局部In颗粒生长过快使Zn-In合金均匀性变差;Zn-In合金中的In能提高Zn电极的析氢过电位,增加Zn阳极溶解电阻,可有效抑制Zn自腐蚀共轭反应的两支;当Zn活化溶解时,In的存在还提供了骨架的作用,为OH~-通过合金表面跟内层的Zn反应提供了通道,使得Zn的致钝电位发生正移,活化电位区间也得到拓宽,Zn的钝化得到延缓,放电深度得到加强,放电容量得到提高;Zn的活化溶解产物易于在In电极表面还原,Zn的充放电性能得到改善.