镁合金表面前处理浸锌工艺及电镀铝研究

重点研究了镁合金前处理过程中浸锌工艺参数对浸锌效果的影响及电镀时电流密度对铝镀层品质的影响.利用SEM及EDS分析了浸锌层及镀层的表面形貌、断面形貌,结合力学性能和成分分析,确定了镁合金前处理方案及后序电镀时的电流密度.结果表明,选取ZnS4-K4P2O7体系浸锌液浸锌,在75℃时浸锌7 min可以得到较好的浸锌层,电镀时采用为3.5～4.0 A/dm2的电流密度得到的铝镀层结合性能好、均匀致密、纯度高.     

AZ31镁合金离子液体镀铝前处理

通过优化镁合金活化及浸锌前处理工艺,在前处理后的镁合金AZ31表面上实施电镀铝。采用SEM/EDX以及极化曲线等手段对镁合金表面上的膜层或镀层进行表征。结果表明,可用于离子液体电镀铝的镁合金前处理工序为碱洗、酸洗、HF活化（400mL/L40%HF,10min）、浸锌（20min）、除水工序。通过该工序,可在镁合金表面上获得致密的浸锌层。采用TMPAC-AlCl3离子液体直流电镀铝,可获得致密的银白色电镀铝层。     

前处理工艺对AZ31镁合金浸锌层性能的影响

浸锌是镁合金电镀与化学镀之前的重要工艺,浸锌层的质量直接影响电镀层或化学镀层的性能。本工作采用扫描电镜(SEM)、动电位极化曲线等方法研究了酸洗和活化工艺对镁合金浸锌层质量的影响。结果表明,最优的酸洗工艺为:30ml/L 65%HNO3+0.5g/L硫脲,室温,时间20s;最优的活化工艺为:375ml/L HF(40%),室温,时间10min;经优化工艺前处理浸锌后能够得到晶粒细小均匀的浸锌层,而且浸锌层与基体结合良好,耐蚀性优良。     

钨铜箔片表面电沉积铝工艺的研究

利用AlCl3+LiAlH4-四氢呋喃-苯体系有机电镀液在自制W90Cu10箔片上镀铝,成功获得了高质量的镀铝层,分析了AlCl3与LiAlH4的配比、电流密度和电镀时间对镀层微观形貌、物相组成及厚度的影响,并得出了这3种影响因素的最佳取值。分析结果表明:铝镀层呈现锥状颗粒生长特征,表面颗粒排列紧密,镀液中AlCl3相对于LiAlH4的含量越少,电流密度越大,则表面颗粒越粗大;电镀时间越长,镀层颗粒在(220)方向择优生长越突出;可通过控制电流密度和电镀时间来控制铝镀层厚度,但若电流密度过高或电镀时间过长,镀层易出现裂纹、枝晶等缺陷。     

电流密度对脉冲电镀Zn-Ni-Mn合金镀层的影响

通过脉冲电镀技术在Q235钢基体上制备出Zn-Ni-Mn合金镀层。研究了电流密度对镀层表面形貌、成分、沉积速率及耐蚀性的影响。结果表明,随着电流密度的增大,沉积速率先增大再减小;镀层中锰含量升高,锌、镍含量降低。随电流密度增加,该镀层随耐蚀性先增强后减弱。电流密度为3.0 A·dm~(-2)时,所得Zn-Ni-Mn合金镀层平整致密,耐蚀性最好。Zn-Ni-Mn合金镀层在3.5%NaCl溶液中的耐蚀性比在5.0%NaOH溶液中更好。     

AZ31镁合金电镀前处理工艺研究

采用扫描电子显微分析、失重实验等手段和方法探讨AZ31镁合金电镀前处理工艺。结果表明,采用CrO₃+Fe(NO₃)₃+KF酸洗后试样表面光亮,基本无失重;采用H₃PO₄+NH4HF活化,可有效去除试样表层氧化物,增强基体和浸锌层的结合力;采用硫酸盐浸锌工艺可获得致密的浸锌层。通过分析温度、电流密度、pH值对浸锌层的影响规律,获得了最佳的浸锌工艺：30g/L ZnSO_4?7H₂O, 150 g/L K₄P₂O₇10H₂O,7 g/L KF, 5g/L Na₂CO₃, 温度70℃～75℃, pH=10.2～10.4 ,浸锌时间10 min。在此前处理基础上电镀锌,镀层和基体结合力较好。     

CLAM钢表面室温离子液体电镀铝

采用AlCl_3-EMIC离子液体在室温下对国产低活性铁素体/马氏体钢(CLAM钢)表面进行镀铝处理。研究了镀前处理对镀层-基体界面的影响。采用SEM、EDS分析了不同电流密度对镀层表面形貌与界面形貌的影响,同时与脉冲电镀所得结果进行了比较。结果表明:在电化学前处理过程中,增大电流密度会增强镀层与基底结合力;电流脉冲的加入可以减弱溶液浓差极化现象,增加表面组织致密性;镀层晶粒大小随电流密度增大而减小,镀层球状组织随电流密度增大而增大。在优化的电镀工艺下(前处理电流密度控制在10 mA/cm~2以上,电镀电流密度控制在10~20 mA/cm~2,对应的电镀时间45~95 min,优选脉冲电流电镀),得到的铝镀层表面光滑,致密,结合力强,厚度可控。     

前处理工艺对镁合金化学镀Ni-P质量的影响

采用扫描电镜和性能检测的方法,分析了表调、活化和浸锌等前处理工艺对镁合金化学镀Ni-P质量的影响.结果表明,表调可使晶界凸出于α-Mg基体,降低镁合金的表面粗糙度,提高化学镀层的结合强度.活化及浸锌后,促进了化学镀的进行.按表调、活化、一次浸锌、退镀、二次浸锌的工艺进行前处理后实施化学镀,得到的Ni-P镀层致密、平整,与基体结合力强,有效提高了镁合金表面耐蚀性及显微硬度.     

AM60镁合金活化及对电镀效果的影响

对AM60镁合金轮毂材料进行了活化工艺研究,采用金相法、3.5%NaCl溶液浸泡试验、划格试验研究了AM60镁合金活化对电镀效果的影响.结果表明,三种活化工艺都是在去除镁合金基体表面的氧化膜和氢氧化膜后形成新的含微孔的保护性膜,控制浸锌和电镀的速度,得到质量更好的镀层.焦磷酸钾活化的效果最好,当K4P2O7·3H2O的浓度为120～200 g/L、Na2CO3为10～30 g/L、KF·2H2O为11 g/L时,电镀镍层耐蚀性好,结合力强.     

AZ31B镁合金表面电镀铝锰合金的耐蚀性

在镁合金AZ31B表面通过预镀锌处理后采用无机熔盐电沉积铝锰合金。使用SEM、EDX和XRD分析镀层的表面形貌、成分和组织,采用动电位极化曲线及表面显微硬度测量考察了镀层对镁合金耐蚀耐磨性的影响。结果表明,熔盐成分、电流密度和熔体温度等典型工艺参数对铝锰合金镀层的形貌、成分和组织都具有重要的影响,进而影响了镀层的耐蚀性。镁合金电镀铝锰合金后,腐蚀电位有很大的提高, 而腐蚀电流密度大幅度的下降;同时铝锰合金镀层表现出很高的硬度,显著的提高了镁合金的耐蚀耐磨性。     

(Zr55All0Ni5Cu30)0.97Ce0.03非晶合金在含Cl-介质中的腐蚀电化学行为研究

  用电化学技术方法研究了Zr₅₅Al_l0Ni₅Cu₃₀和(Zr₅₅Al_l0Ni₅Cu₃₀)_0.97Ce_0.03非晶合金在含Cl^-介质中的腐蚀电化学行为及添加稀土Ce的影响.结果表明：随Cl^-浓度增加,两种非晶合金的腐蚀速度加快;添加稀土Ce后提高合金耐蚀性;随极化电位的提高,两种非晶合金在0.05 mol/L Na₂SO₄及含Cl^-介质中均出现钝化特征,维钝电流密度随Cl^-浓度增加而减小;Zr₅₅Al_l0Ni₅Cu₃₀非晶合金的电化学阻抗谱由单容抗弧组成(Zr₅₅Al_l0Ni₅Cu₃₀)_0.97Ce_0.03非晶合金的交流阻抗谱在Cl^-浓度较低时呈单容抗弧特征,而随Cl^-浓度的增加,单容抗弧变为双容抗弧.     

由电热法一次铝硅合金制取铸造铝硅合金的研究

由电热还原法制取的一次铝硅合金含有铝55%.硅25%和一些杂质.其中的杂质主要是铁和一些金属氧化物.在实验室中研究了由一次铝硅合金制取铸造铝硅合金的工艺.研究结果得出,使用含冰晶石和氯化钠混合物的精炼剂以及金属锰为除铁剂并采取适当的工艺方法,可以有效地去除一次铝硅合金中的杂质,制取符合工业标准的铸造铝硅合金.文中对精炼剂量的大小以及过滤温度等工艺条件对铸造合金中某些金属杂质含量的影响进行了研究.     

Zn-Al伪合金涂层的耐蚀性能研究

目的提高电弧喷涂锌铝合金涂层中Al的含量。方法用纯铝丝和Zn80Al20合金丝在Q235钢表面制备Zn-Al伪合金涂层,通过中性盐雾试验和电化学试验,与纯铝涂层和Zn-Al合金涂层进行对比,分析比较三种涂层在氯离子存在环境中的腐蚀行为。结果 Zn-Al伪合金涂层表现出了较高的活化能力和较低的腐蚀速度。结论 Zn-Al伪合金涂层的耐蚀性能优于纯铝涂层和Zn-Al合金涂层。     

Interface electrochemical corrosion behaviour of alclad Al–Zn–Mg–Cu–Cr Al alloy adhesively bonded with carbon fibre reinforced plastic stiffener

Abstract

Stiffening of Al alloy aircraft structures with carbon fibre reinforced plastic laminate called ‘patches’ is considered as a viable option to enhance fatigue life. Interface so created between the reinforcement and Al alloy structure is potential site for crevice corrosion attack. Therefore, studies were conducted to investigate the interface corrosion behaviour of peak and two-step aged Al–Zn–Mg–Cu–Cr alclad alloy with and without the patch and examine the possibility to control the interfacial attack with the addition of cerium chloride inhibitor exposed to 3·5 wt-% NaCl solution for the durations of 2 and 168 h. Electrochemical impedance spectroscopy revealed that the interface attack was significantly reduced by the addition of 1000 ppm cerium chloride. The response of the peak and two-step aged alloy for such an addition was further investigated and found that the alloy under step aged condition behaves better than that of the peak aged condition.     

Microstructure and formation mechanism of Ce-based chemical conversion coating on 6063 Al alloy

In order to accelerate the conversion coating formation on 6063 Al alloy in the Ce(NO3)3 solution, accelerants of chloride and ammonium salt were used. The coating morphology, composition and structure were analyzed with SEM/EDS, EPMA, XPS and XRD. The coating morphology is influenced by the composition, pH value and temperature of the treating solution. The coating composed of metal oxide, metal hydroxide and hydrate appears to be amorphous. The elements in the coating are Al, Ce, O, Mn and Mg, while the Ce element exists in the forms of Ce3+ and Ce4+. The accelerant of chloride can increase the compactness and Ce content of the coating, so the coating corrosion resistance is remarkably improved. A scheme for the electrochemical reaction in the coating formation was proposed, and the potential change in the coating formation was also studied. It is found that chloride can shorten the time period of the first and the second stages in coating formation.     

Zn–Al layered double hydroxides as chloride nanotraps in active protective coatings

Zn–Al layered double hydroxides (LDHs) intercalated with nitrate anions are suggested as chloride nanotraps for organic polymeric coatings. The addition of such nanotraps to a polymer layer drastically reduces the permeability of corrosive chloride anions through the protective coatings. In solution, Zn(2)–Al–NO₃ LDHs are responsive to the concentration of chlorides and the release of nitrates is accompanied by entrapment of chlorides, with the process governed by ion-exchange equilibrium. In particular, a coating modified with LDH–NO₃ was found to exhibit significantly lower permeability to chlorides when compared to both unmodified and LDH–Cl-containing coatings, which proves the applicability of LDHs in delaying coating degradation and corrosion initiation.     

表面涂少量氧化锰提高Ti47Al2Cr2Nb合金高温抗氧化性

研究了表面涂少量MnCl2对Ti47Al2Cr2Nb合金900℃恒温氧化行为的影响。涂少量MnCl2后合金的氧化速率降低了50%以上,氧化膜也由TiO2和Al2O3的混合物变为以Al2O3为主的氧化物。发生上述变化的原因可能在于氧化开始时合金中钛与Cl反应形成钛的亚稳态氯化物挥发掉,合金表面形成一层致密的氧化铝膜,阻碍合金中的Ti向外扩散氧化,因此提高了合金的高温氧化性能。     

表面涂少量氯化锰提高Ti47Al2Cr2Nb合金高温抗氧化性

研究了表面涂少量ＭｎＣｌ２ 对Ｔｉ４７Ａｌ２Ｃｒ２Ｎｂ 合金９０００Ｃ 恒温氧化行为的影响。涂少量ＭｎＣｌ２ 后合金的氧化速率降低了５０ ％ 以上,氧化膜也由ＴｉＯ２ 和Ａｌ２Ｏ３ 的混合物变为以Ａｌ２Ｏ３ 为主的氧化物。发生上述变化的原因可能在于氧化开始时合金中钛与Ｃｌ 反应形成钛的亚稳态氯化物挥发掉,合金表面形成一层致密的氧化铝膜,阻碍合金中的Ｔｉ 向外扩散氧化,因此提高了合金的高温抗氧化性能     

Corrosion behavior of aluminum weld overlay alloys with dispersed niobium carbide particles in sodium chloride solution

Aluminum overlay weld alloys with dispersed niobium carbide particles (NbCp/Al) were prepared by a plasma transferred arc welding process. The corrosion behavior of the NbCp/Al alloys was studied in sodium chloride solution by means of electrochemical techniques and scanning electron microscopy. The aluminum alloys under investigation were pure aluminum, aluminum-magnesium, aluminum-magnesium-silicon, and aluminum-copper. The addition of NbC particles shifted the corrosion potentials in the positive direction. However, the pitting potentials were almost similar to that of overlay weld alloy without NbC particles. In the immersion test in quiescent 0.5M NaCl open to the air, preferential localized corrosion of all NbCp/Al alloys was observed at the matrix between NbC particles and crystalline phases.     

Influence of temperature and chloride ion concentration on the corrosion behaviour of Mg–4Al–3Ca–0.5RE alloy

The influence of temperature and chloride ion concentration on the corrosion behaviour of Mg?4Al?3Ca?0.5RE alloys were studied in this paper. Corrosion rates of the alloys were measured by weight loss test and electrochemical measurement. The results revealed that a shorter incubation period to the onset of corrosion, a more negative corrosion potential, and a higher corrosion rate was correlated with a higher temperature in 3% NaCl solution and a higher chloride ion concentration at 30°C. The corrosion behaviour of the alloys was affected by surface film and the corrosion mainly occurred at the breaks or defects in surface films.