铝箔表面化学镀锌对其在HCl-H 2 SO 4体系中电蚀性能的影响

将高压铝电解电容器用电子铝箔在含Zn2＋的5.0%NaOH溶液中实施化学镀锌处理,然后在HCl＋H2SO4电解液中进行直流电解扩面腐蚀得到腐蚀箔;采用极化曲线研究化学镀锌处理对扩面腐蚀时铝箔点蚀电流、点蚀电位的影响,利用电化学交流阻抗（EIS）研究化学镀锌处理对铝箔电解腐蚀时电化学特征的影响;使用扫描电镜（SEM）观察化学镀锌处理对腐蚀箔表面和横截面形貌的影响;测试100 V形成电压下腐蚀箔的比电容。结果表明：铝箔表面化学镀锌形成的Zn-Al微电偶有助于电蚀时降低点蚀电极反应的阻力,提高点蚀电流密度,增加铝箔表面蚀孔密度和蚀孔分布的均匀性;随着碱液中Zn2＋浓度的提高,腐蚀箔的比电容逐渐增加。     

电解工艺条件对铝箔腐蚀形貌与比电容的影响

利用扫面电镜(SEM)、数字电桥研究了铝电解电容器用高压电子铝箔在硫酸+盐酸体系中进行电化学腐蚀扩面时,工艺条件对铝箔腐蚀形貌与比电容的影响规律:电解腐蚀时间对铝箔腐蚀后形貌与比电容影响较大,发孔时间延长、扩孔时间缩短,隧道孔密度增加、孔直径减小;发孔电流密度对铝箔腐蚀形貌与比电容影响较小,只要高于点蚀电流密度,小电流长时间发孔与大电流短时间发孔都可以在铝箔表面形成足够密度的蚀孔结构;电解液温度对铝箔腐蚀形貌和比电容影响较大,随着发孔液温度的提高,蚀孔密度增加、蚀孔孔径减小,隧道孔长度减小.     

咪唑啉缓蚀剂对电解电容器用铝箔直流扩面增容的作用

合成了油酸咪唑啉和丙烯酸咪唑啉化合物,通过红外谱对其进行了结构表征;用Tafle曲线和交流阻抗等方法研究了其对铝箔的缓蚀作用,并研究了其对铝箔直流扩面增容的影响。结果表明,在2.0 mol/L的HCl溶液中两种化合物对铝箔均有缓蚀作用,为阴极型缓蚀剂,腐蚀液中添加两种化合物后,铝箔直流扩面的蚀孔密度增加、分布均匀、使铝箔的比电容提高约25%。     

缓蚀剂对高压铝箔电蚀特征的影响

利用扫描电镜分析了盐酸+硫酸混合酸电解液中添加适量缓蚀剂聚乙二醇或聚丙烯酸对高压铝箔电解腐蚀后表面形貌与横截面形貌的影响,利用LCR仪与电子天平测试了铝箔比电容与质量失重率。结果表明:缓蚀剂可以改善电解腐蚀后铝箔表面隧道孔孔径的分布,使隧道孔由圆锥状转变为圆柱状,降低隧道孔的并孔团簇现象,这有利于提高铝箔电解腐蚀扩面后的实际表面积;同时铝箔的实际质量失重率明显降低,铝箔的比电容显著增加。     

基于方差分析的铝箔电解扩面腐蚀

应用正交实验方差分析研究了高压铝电解电容器用铝箔电解扩面腐蚀时,发孔腐蚀液中H2SO4浓度、HCl浓度、温度、电解电流密度和电解腐蚀时间对铝箔腐蚀扩面效果的影响;采用扫描电镜观测和极化曲线测试研究了发孔腐蚀液中H2SO4浓度变化对腐蚀铝箔表面形貌、横截面形貌以及电蚀发孔点蚀能力的影响。结果表明:腐蚀液中H2SO4浓度是最重要的影响因素,随着H2SO4浓度的增加,极化曲线上点蚀电流密度减小、发孔密度降低、隧道孔长度减小、并孔程度减轻,在本研究范围内,较佳的腐蚀工艺条件为:盐酸浓度1.4 mol·L-1、硫酸浓度3.2 mol·L-1、温度73℃、电流密度0.30 A·cm-2、时间50 s。     

酸碱预处理对阳极铝箔电蚀特征的影响

利用扫描电镜研究了高压铝箔在75℃、6%HCl溶液、40℃、0.5%NaOH溶液和40℃、10%NaCl溶液中分别进行1min预处理后对其电蚀特征与化成箔比电容的影响。结果表明,酸洗、碱洗可以提高电蚀时蚀孔萌生密度,改善蚀孔分布均匀性,提高电蚀后铝箔表面积与比电容。     

最终退火工艺和腐蚀预处理对铝箔发孔性能的影响

通过极化曲线测试铝箔的腐蚀电位,结合光学显微镜和扫描电镜等观察铝箔腐蚀发孔后的表面形貌,探讨最终退火工艺和酸碱预处理对高压电子铝箔腐蚀发孔性能的影响规律。结果表明:铝箔在经不同温度(470～560℃)和不同时间(0.5h～4h)的最终退火处理时,当铝箔经500℃,1h退火后,各种有利于发孔的元素扩散到铝箔表层、富集并且均匀分布,此时的发孔效果最好,继续升高退火温度和延长退火时间反而会使发孔变得不均匀;发孔前碱处理能适当减少铝箔表面的氧化层,酸处理则将Cl-引入铝箔表面,酸+碱清洗使铝箔的腐蚀电位降低,促进铝箔的腐蚀发孔,腐蚀后的发孔面积和密度比未经预处理的大,发孔更均匀。     

浸渍丙烯酸树脂处理对阳极铝箔腐蚀特性及形貌的影响

为避免过度腐蚀,使铝箔产生较均匀、密集的隧道孔,增大铝箔比表面积、提高比电容,先在铝箔表面浸渍丙烯酸树脂,再在直流电作用下对铝箔进行电蚀发孔,分析铝箔减薄率和失重率,用金相显微镜(OM)对腐蚀铝箔断面进行检测。结果表明,在丙烯酸树脂质量分数为0%~1.5%范围内,铝箔浸渍丙烯酸树脂处理对阳极铝箔腐蚀形貌的改善产生积极作用,并随丙烯酸树脂质量分数增大,铝箔减薄率和失重率呈现先减小后增大趋势;去用质量分数为0%~15%的丙烯酸树脂浸渍处理,随丙烯酸树脂浓度的增大,腐蚀铝箔减薄率出现负下降;用丙烯酸树脂质量分数为0.6%浸渍后的腐蚀铝箔,能产生数量较多、孔长较长、分布较均匀、竖直的隧道孔,铝箔比表面积增大、比容相对增加,因此较佳的浸渍液的丙烯酸树脂质量分数约为0.6%。     

双阴极电解腐蚀工艺对阳极铝箔侵蚀性能的影响

为改善阳极铝箔腐蚀形貌,增大腐蚀比表面积,减少铝箔的质量损失,采用在直流电作用下,外加垂直于铝箔的石墨板与原有石墨板共同构成腐蚀阴极,铝箔为阳极,在H_2SO_4和HCl混酸中进行电蚀发孔,对腐蚀铝箔的失重率,减薄率进行分析,用扫描电镜(SEM)检测铝箔腐蚀后形貌。结果表明,在直流电蚀工艺下,通过调整阴极极板面积和放置方式,铝箔表面能产生较均匀、浅而长的表面隧道,且在表面隧道中,能继续形成点蚀孔,使腐蚀铝箔比表面积增大,比容相对增加;一定腐蚀时间范围内,腐蚀时间对铝箔减薄率影响很小,腐蚀时间适应范围较宽,有利于工艺调整;最佳的电解腐蚀工艺参数为:腐蚀温度80℃、腐蚀电流密度0.10 A/cm~2、腐蚀时间120 s。     

高压电子铝箔阳极电解扩孔行为

研究发孔铝箔在盐酸和硝酸溶液中的阳极极化行为与扩孔特性的关系。阳极扩孔的基本条件是将发孔箔的内、外表面都控制在钝化状态下。在盐酸溶液中,阳极极化时存在点蚀电位和一个较小的钝化电位区,当扩孔施加的电流密度大于临界点蚀电流密度时,铝箔表面发生二次发孔,导致形成孔蚀族与并孔,腐蚀箔厚度减薄,比电容显著降低。在硝酸溶液中,阳极极化时存在一个宽阔的钝化电位区,因此硝酸扩孔比盐酸扩孔容易控制,不会发生二次发孔。提高盐酸或硝酸浓度与温度均可以增大最大维钝电流密度,即增大扩孔的最大电流密度,提高扩孔的生产效率。     

Effect of pretreatment on electrochemical etching behavior of Al foil in HCl–H2SO4

The aluminum foil for high voltage aluminum electrolytic capacitor was immersed in 0.5 mol/L H₃PO₄ or 0.125 mol/L NaOH solution at 40 °C for different time and then DC electro-etched in 1 mol/L HCl+2.5 mol/L H₂SO₄ electrolyte at 80 °C. The pitting potential and self corrosion potential of Al foil were measured with polarization curves (PC). The potentiostatic current—time curve was recorded and the surface and cross section images of etched Al foil were observed with SEM. The electrochemical impedance spectroscopy (EIS) of etched Al foil and potential transient curves (PTC) during initial etching stage were measured. The results show the chemical pretreatments can activate Al foil surface, facilitate the absorption, diffusion and migration of Cl^? onto the Al foil during etching, and improve the initiation rate of meta-stable pits and density of stable pits and tunnels, leading to much increase in the real surface area and special capacitance of etched Al foil.     

Effects of polymer corrosion inhibitor on widening etch tunnels of aluminum foil for capacitor

We investigated the effects of polymeric corrosion inhibitor polystyrene sulfonic acid (PSSA) additive to 3% HNO₃ solution on widening tunnels of pre-etched aluminum foil by electrochemical DC etching for aluminum electrolytic capacitors, using scanning electron microscopy and polarization curves. With trace PSSA, the dissolution of exterior surface of etch tunnels of Al foil is suppressed and the dissolution of interior surface of etch tunnels of Al foil is facilitated, respectively. The tunnels transform from circular cone to circular column in shape and pits-merging on the surface is weakened, leading to significant increase in the surface area and specific capacitance of the Al foil. The amounts of reduced thickness and weight of Al foil during the widening process of etch tunnels can be decreased if PSSA is employed.     

Elektrolytische Tunnelätzung von Aluminiumfolie

Electrolytic tunnel etching of aluminium foil The most effective method of etching aluminum foil for high voltage electrolytic capacitors is the electrolytic tunnel etching with direct current in an aqueous solution of chloride salts. Surprisingly the classical electrochemical method for determining the potentiostatic current-time curves of annealed high purity aluminum foil delivers a pure tunnel etching in a narrow range around the pitting potential. The potentiostatic current-time curves show the dynamic of the very fast and on an already etched aluminum foil not repeatable process of forming the tunnels (tunnel diameter ca. 0.2 μm; tunnel length 10–100 μm) and immediate after tunnel formation the about 1000 times slower and controllable process of widening these tunnels in the region of passivation current density.     

ECAP变形后超硬铝合金的电化学腐蚀行为

采用电化学测量技术,研究了等径转角挤压方法(ECAP)变形后的AA7075-T651铝合金在NaCl溶液中的电化学腐蚀行为。结果表明:同道次ECAP状态下,随着Cl-浓度增加,AA7075-T651的自腐蚀电位和点蚀电位负移,耐腐蚀性能降低;而在同浓度NaCl溶液中,随着ECAP挤压道次增加,AA7075-T651的自腐蚀电位和点蚀电位正移,耐腐蚀性能提高。本次试验也表明了Cl-浓度对于该铝合金耐腐蚀性能的影响程度要远超过ECAP技术。     

磁致涡流效应对阳极铝箔形貌及比电容的影响

针对盐酸-硫酸体系,通过耦合外加磁场对铝箔进行直流电化学腐蚀,系统研究磁致涡流效应(MagnetoHydrodynamics,MHD效应)对铝箔电化学行为、界面行为以及质量传递的影响。采用X射线衍射(XRD)、低温氮气吸附、扫描电镜(SEM)等手段对腐蚀箔样品进行表征。同时,通过计时电位法、极化曲线、循环伏安法、电化学阻抗法研究MHD效应对铝箔电化学性能的影响。结果表明,MHD效应能够抑制氧化膜的生长,增加铝箔表面Cl-的吸附量,减小扩散层厚度,强化Cl-/Al3+向孔内/孔外的传质,减小电解液中离子传递阻力。通过引入磁场,明显提高了腐蚀箔的蚀孔密度、平均孔径以及平均蚀孔深度的均一性,继而增大了阳极电子铝箔的比电容。     

Surface Characterization of 7075-T73 Aluminum Exposed to Anodizing Pretreatment Solutions

Localized corrosion damage in Type 7075-T73 aluminum alloy was investigated for various anodizing pretreatment solutions. The postexposure surface corrosion was characterized by use of scanning electron microscopy (SEM) examination. In addition, SEM and energy dispersive spectroscopy (EDS) were used for second-phase (constituent) particle identification for those found to induce pitting corrosion during solution exposure. The pitting mechanisms were identified as circumferential where the particles are noble with respect to the matrix phase and by selective dissolution where they are anodic. The designated category-1 degreasing and category-2 inhibited alkaline solutions did not initiate localized corrosion after 1200 s exposures. However, the category-3 high-pH NaOH and category-4 low-pH HNO₃ based solutions were found to initiate pitting attack, with the NaOH being significantly more aggressive. It was hypothesized that if the pits initiating during the pretreatment exposures were beyond a threshold size, on the order of 10-20 μm, a higher current density existed at these locations during subsequent electrochemical processes, thus resulting in larger and deeper pit structures. These surface defects are of primary concern with respect to accelerated fatigue crack nucleation. For smaller pits, on the order of 1-5 μm, the anodic process had a smoothing affect where the film growth tended to passivate the pits.