6061铝合金氟钛酸盐转化膜耐蚀性能的改性研究

采用单因素试验研究了氟硅酸铵、络合剂及缓蚀剂对6061铝合金表面氟钛酸盐转化膜耐蚀性能的影响。结果表明,最佳的转化液成分及转化条件为:氟化钠3g/L,氟硅,酸铵4g/L,六偏磷酸钠1.0g/L,钛盐1.5g/L,H2O21.5ml/L,常温下转化处理10min,处理液pH 5.0。采用SEM,EDS和极化曲线方法测试了改性后转化膜的形貌及耐蚀性。结果表明,改性后的氟钛酸盐转化膜由连续而致密的晶体颗粒组成;氟钛酸盐转化膜使6061铝合金的自腐蚀电位增加了77mV,转化膜的腐蚀电流密度降低了约80%;6061铝合金的耐蚀性能明显得到提高。     

6063铝合金中性无铬转化膜制备及膜层性能分析

目的 提高铝合金微小器件的耐蚀性,开发一种条件温和可控的转化膜成膜工艺。方法 采用中性无铬转化工艺,在6063铝合金表面制备转化膜。通过研究NaF、NH₄HF₂、KMnO₄、十二烷基硫酸钠(SDS)和没食子酸等几种添加剂对转化膜外观与耐蚀性的影响,确定NH₄HF₂为最佳添加剂。采用电化学方法分析膜层的耐蚀性,用SEM和EDS分析表面形貌及元素组成,并采用XRD和XPS表征膜层晶态结构和化合物组成。基于检测结果,简要分析转化膜的成膜过程。结果 最终得到了中性转化处理的最佳成膜工艺为EDTA-2Na 8.0 g/L,单宁酸1.0 g/L,Na₂WO₄ 6.0 g/L,H2Zr F6 4.0 g/L,NH₄HF₂ 3.0 g/L,p H 6.6,成膜温度为30℃,成膜时间为15 min。该工艺所制备的转化膜外观致密均匀,颜色为浅黄色。电化学测试结果表明,转化膜具有良好耐蚀性,自腐蚀电流密度由基体铝...     

LY12铝合金的锰酸盐导电化学转化膜制备与表征

以KMnO4为主盐,Na2ZrF6作促进剂,研究了LY12铝合金锰酸盐化学转化膜的制备工艺,采用点滴法和膜接触电阻法评价转化膜的耐蚀性和导电性,并用SEM,EDS和XRD表征转化膜的形貌与组成,进而探讨成膜机理。结果表明:当KMnO4的质量浓度为5 g/L,Na2ZrF6的质量浓度为0.05 g/L,pH值2.0,温度65℃,转化时间60 s、沸水后处理30 min时,所制备的锰酸盐转化膜颜色呈金黄色,该膜层均匀、致密,主要成分为Al,O,Mn元素,由铝和锰的氧化物组成。LY12铝合金表面的锰酸盐化学转化膜耐蚀性和导电性明显提高,点滴法耐腐蚀时间达到57 s,转化膜表面接触电阻仅为铝合金基体接触电阻的15.6%。     

铝合金表面碱性化学镀镍工艺研究

为了改善铝合金表面的可钎焊性能,采用碱性化学镀镍工艺在6063铝合金表面进行化学镀镍.通过正交试验方法对碱性化学镀镍工艺进行了优化,并获得了具有良好钎焊性能的化学镀镍层.采用扫描电镜和能谱分析等手段,分析了化学镀镍层的成分和组织形貌.研究结果表明,有利于明显提高化学镀镍层钎焊性能的最佳配方和工艺为:5g/L硼酸、30g/L硫酸镍、30g/L次亚磷酸钠,温度50℃.     

ADC12铝合金表面钴盐黑色化学转化膜的制备及耐蚀性研究

以硝酸钴为主盐,通过正交实验和单因素实验在ADC12铝合金表面制备了黑色转化膜。获得的最优工艺条件为:高锰酸钾5.0g/L,硫酸1.5ml/L,硝酸钴30.0g/L,处理时间12min,温度65℃。制备的钴盐转化膜色泽均匀,膜层致密完整,转化膜由Al_2O_3、Co_2MnSi、Co_2O_3等物相组成,其中Al_2O_3是主要组成相。转化膜重铬酸钾点滴时间达到4 min,经5%浓度的NaCl水溶液浸泡168h后出现轻微点腐蚀,电化学测试表明腐蚀电位正移,腐蚀电流降低约3倍,结果表明钴盐转化膜具有良好的抗腐蚀性能。     

你问我答

怎样在铝上浸锌镍合金及镀硬铬?答:铝及铝合金制件经碱蚀和酸洗出光后,就可以进行浸锌-镍合金(二次法)处理。其合金液组成及工艺条件为:120g/L氢氧化钠,40g/L硫酸锌,40g/L酒石酸钾钠,30g/L硫酸镍,5g/L硫酸铜,10g/L氰化钾,2g/L三氯化铁。第一次浸锌-镍合金(时间40～60s)后,在1∶1硝     

铝合金表面锡盐转化膜的制备及其耐蚀性

以硫酸亚锡为主盐,通过化学转化法在铝合金表面形成耐蚀性良好的无铬化学转化膜。考察了锡盐浓度、成膜氧化剂浓度、成膜促进剂的质量浓度、反应温度及反应时间对膜层耐蚀性的影响,并对转化膜的耐蚀性能进行了电化学测试。在pH值为2～3时,确定了无铬化学转化液膜的最佳制备条件:SnSO40.15 g/L、KMnO41.5 g/L、NaF 2 g/L,反应温度30℃,反应时间1.5 min;该转化膜制备工艺简便、成膜速度快,膜的耐蚀性能好。     

Mn~(2+)浓度对6063铝合金表面锆基转化膜组织和耐蚀性的影响

为了改善6063铝合金表面锆基转化膜的耐腐蚀性能,利用XRD、SEM、EDS及电化学腐蚀等方法研究了促进剂中Mn~(2+)浓度对6063铝合金表面锆基转化膜的组织和耐蚀性的影响。结果表明,当促进剂中ρ(Mn~(2+))=2.2 g/L浓度时,锆基转化膜比不添加Mn~(2+)时的更致密,但是ρ(Mn~(2+))=4.4 g/L时,转化膜致密性反而下降,不过Mn~(2+)浓度对转化膜厚度的影响不大。本试验制备的锆基转化膜与铝合金基体无明显分界,表明锆基转化膜与铝基体结合良好。并且所制备的转化膜表面属于多孔结构,有利于提高膜与喷涂油漆的附着力。电化学腐蚀性表明,当采用ρ(Mn~(2+))=2.2 g/L Mn~(2+)浓度的促进剂时,转化膜的腐蚀电流密度变小,大约是没有添加Mn~(2+)的1/200,而且极化电压增加,大约是没有添加Mn~(2+)的8.7倍。这些参数表明,Mn~(2+)的加入提高了锆基转化膜的耐腐性。但是Mn~(2+)浓度过大会导致耐腐性下降,甚至不如没有添加Mn~(2+)的转化膜的。     

6063 铝合金表面 Ce-Mn / Mo 复合转化膜的制备及性能

目的进一步改善6063铝合金表面Ce-Mn转化膜的综合性能。方法采用以Ce(NO3)3和KMn O4为主盐的转化液,在6063铝合金表面制备出Ce-Mn转化膜,再利用钼酸钠溶液进行后处理,优化处理工艺,获得Ce-Mn/Mo复合转化膜。对后处理前后的转化膜形貌、成分及电化学性能进行对比,并通过空气中放置、磨损测试的方法对比它们的耐候性和耐磨性。结果较优的成膜工艺为:18 g/L Na2Mo O4,1.5 g/L十二烷基苯磺酸钠,成膜时间18 min,成膜温度45℃。经后处理后,膜层颜色由金黄色转变为棕黑色,组织致密,主要由Ce,Mn,Mo,O和Al等元素组成,厚度提高至约7μm,腐蚀电流密度降低了约85%。结论与Ce-Mn膜层相比,Ce-Mn/Mo复合转化膜具有更优异的耐蚀性、耐候性和耐磨性。     

6063铝合金的碱性化学抛光

传统的铝合金"三酸"化学抛光液中含有硝酸组分,在抛光过程中会产生大量的黄烟,造成环境污染,危害人体健康。对6063铝合金的碱性化学抛光液配方和工艺条件进行了试验研究。结果表明:抛光液配方中的NaOH是影响抛光光亮度的主要因素,NaOH浓度越高,抛光效果越好;其次是温度,温度越高效果越好;NaNO_3具有较好的辅助抛光作用。通过进一步试验优化出6063铝合金碱性化学抛光液配方为,NaOH 400 g/L,NaNO_3(150～200)g/L,NaH_2PO_410 g/L,Na F 60 g/L,Na_2SiO_3·9H_2O 20 g/L,CH_4N_2S 10 g/L。抛光温度110℃,抛光时间60 s。     

AZ91D 镁合金 Mo-Mn 无铬转化膜的制备与耐蚀性

目的通过Mo-Mn无铬转化膜提高AZ91D镁合金的表面耐蚀性。方法采用正交实验法,研究不同浓度的NaMoO4和KMnO4以及温度对转化膜的影响。优选实验参数后,考察时间对转化膜的影响。利用SEM及EDS研究转化膜的微观形貌及成分变化,测试转化膜在3.5%NaCl溶液中的极化曲线和交流阻抗谱。结果当NaMoO4和KMnO4的质量浓度分别为10,6 g/L,pH=5,温度为50℃,转化时间为40 min时,转化膜颜色较为均匀,微观裂纹相对较少,自腐蚀电位比镁基体大约提高0.075 V,自腐蚀电流密度比镁基体降低近1个数量级。当Na Mo O4和KMnO4的质量浓度分别为20,8 g/L,pH=5,温度为50℃,转化时间为40 min时,转化膜颜色最为均匀,微观裂纹相对最少,自腐蚀电位比镁基体提高大约0.047 V,自腐蚀电流密度比镁基体降低2个数量级。交流阻抗谱图显示,后一种转化膜试样的极化电阻为1450.2Ω,而镁基体的极化电阻为806.4Ω。结论 Mo-Mn无铬转化膜可以显著提高AZ91D镁合金的表面耐蚀性。     

Effect of anodizing on galvanic corrosion behavior of T300 CFRP/5083P-O Al bolted joints

T300 carbon fiber reinforced polymer (CFRP) and 5083P-O aluminum (5083P-O Al) alloy bolted joints have been used in high-speed trains due to the advantages of light weight and high strength. However, high potential difference between the CFRP and 5083P-O Al will induce galvanic corrosion and result in accelerating corrosion rate of 5083P-O Al, which is a potential risk for its engineering applications. In this work, combination with the electrochemical analysis, surface and cross-section corrosive morphologies analysis, the galvanic corrosion behavior between CFRP/5083P-O Al bolted joints with and without anodizing in 3.5 wt.% NaCl spray was investigated. Results indicated that severe corrosion occurred on unanodized 5083P-O Al in the coupled regions of the CFRP/5083P-O Al bolted joint due to galvanic corrosion. With the content of sulfuric acid increasing, the thickness of each Al₂O₃ layer and atomic oxygen content increases significantly. 5083P-O Al anodized by the 135 g/L H₂SO₄ + 8 g/L H₃BO₃ mixed solution had the favorable Al₂O₃ film, which increased the resistance of 5083P-O Al by roughly three orders of magnitude, effectively improving the corrosion resistance of 5083P-O Al.     

Effect of equal-channel angular pressing on pitting corrosion resistance of anodized aluminum-copper alloy

The effect of equal-channel angular pressing(ECAP) on the pitting corrosion resistance of anodized Al-Cu alloy was investigated by electrochemical techniques in a solution containing 0.2 mol/L AlCl₃ and also by surface analysis. Anodizing was conducted for 20 min at 200 and 400 A/m² in a solution containing 1.53 mol/L H₂SO₄ and 0.018 5 mol/L Al₂(SO₄)₃·16H₂O at 20 °C. Anodized Al-Cu alloy was immediately dipped in boiling water for 20 min to seal the micro pores present in anodic oxide films. The time required before initiating pitting corrosion of anodized Al-Cu alloy is longer with ECAP than without, indicating that ECAP process improves the pitting corrosion resistance of anodized Al-Cu alloy. Second phase precipitates such as Si, Al-Cu-Mg and Al-Cu-Si-Fe-Mn intermetallic compounds are present in Al-Cu alloy and the size of these precipitates is greatly decreased by application of ECAP. Al-Cu-Mg intermetallic compounds are dissolved during anodization, whereas the precipitates composed of Si and Al-Cu-Si-Fe-Mn remain in anodic oxide films due to their more noble corrosion potential than Al. FE-SEM and EPMA observation reveal that the pitting corrosion of anodized Al-Cu alloy occurs preferentially around Al-Cu-Si-Fe-Mn intermetallic compounds, since the anodic oxide films are absent at the boundary between the normal oxide films and these impurity precipitates. The improvement of pitting corrosion resistance of anodized Al-Cu alloy processed by ECAP appears to be attributed to a decrease in the size of precipitates, which act as origins of pitting corrosion.     

The corrosion of Fe3Al alloy in liquid zinc

A systematic study of the isothermal corrosion testing and microscopic examination of Fe₃Al alloy in liquid zinc containing small amounts of aluminum (less than 0.2 wt.%) at 450 °C was carried out in this work. The results showed the corrosion of Fe₃Al alloy in molten zinc was controlled by the dissolution mechanism. The alloy exhibited a regular corrosion layer, constituted of small metallic particles (diameter: 2-5 μm) separated by channels filled with liquid zinc, which represented a porosity of about 29%. The XRD result of the corrosion layer formed at the interface confirmed the presence of Zn and FeZn_6.67. The corrosion rate of Fe₃Al alloy in molten zinc was calculated to be approximately 1.5 × 10⁻⁷ g cm⁻² s⁻¹. Three steps could occur in the whole process: the superficial dissolution of metallic Cr in the corrosion layer, the new phase formation of FeZn_6.67 and the diffusion of the dissolved species in the channels of the corrosion layer.     

The synergistic effect of Na3PO4 and benzotriazole on the inhibition of copper corrosion in tetra‐n‐butylammonium bromide aerated aqueous solution

The effect of Na₃PO₄ and the mixture of benzotriazole (BTA) and Na₃PO₄ (SP) on the corrosion of copper in 17 wt% (0.534 mol/L) tetra‐n‐butylammonium bromide (TBAB) aerated aqueous solution has been investigated by means of weight‐loss test, potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy/energy dispersive X‐ray techniques. The experimental results showed that a dosage of Na₃PO₄ stimulated the copper corrosion, and the corrosion rate increased with increasing Na₃PO₄ concentration, whereas the mixture of BTA and Na₃PO₄ could protect copper in aqueous TBAB solution. The inhibition action of the mixture of BTA and Na₃PO₄ on the corrosion of copper is mainly due to the inhibition of the anodic process of corrosion. The inhibition efficiency of a mixture consisting of 2 g/L BTA and 1 g/L Na₃PO₄ was about 96%. The mixture of BTA and Na₃PO₄ inhibits the corrosion of copper better than BTA by itself, indicating that Na₃PO₄ has a synergistic role with BTA on the corrosion inhibition of copper in TBAB aqueous solution.     

Corrosion properties ofAZ31 magnesium alloy and protective effects of chemical conversion layers and anodized-coatings

The corrosion properties of AZ31 magnesium alloys were studied by potentiodynamic polarization curves and electrochemical impedance spectroscopy（E1S） techniques, meanwhile, the protective properties of two environmentally protective types of chemical conversion layers and anodized coatings of AZ31 magnesium alloys were also discussed. The component of chemical conversion bath is NaH2PO4·12H2O 20 g/L, H3PO4 7.4 mL/L, NaNO2 3 g/L, Zn（NO3）2·6H2O 5 g/L and NaF 1 g/L, and components of the anodization bath is Na2SiO3 60 g/L, C6H5Na3O7·2H2O 50 g/L, KOH 100 g/L and Na2B4O7·2H2O 20 g/L. The results show that the corrosion resistance of AZ31 magnesium increases with the increase of pH value of the corrosive medium. For the chemical conversion layer acquired at 80 ℃, 10 min is the best processing time and the charge transfer resistance of the chemical conversion layer is enhanced nearly by 10 times. The optimum processing time for the anodization of AZ31 is 60 min, the charge transfer resistance value of the anodized sample at the early immersion stage is nearly 26 times of that of the blank sample and the corrosion type of the anodized samples is pitting.     

The high-temperature corrosion behavior of Nb-Al alloys in a H2/H2S/H2O gas mixture

The corrosion behavior of pure Nb and three Nb Al alloys containing 12.5, 25, and 75 at.% Al was studied over the temperature range of 800–1000°C in a H₂/H₂S/H₂O gas mixture. Except for the Nb-12.5Al alloy consisting of a two phase structure of -Nb and Nb₃Al, other alloys studied were single phase. The corrosion kinetics followed the parabolic rate law in all cases, regardless of temperature and alloy composition. The parabolic rate constants increased with increasing temperature, but fluctuated with increasing Al content. The Nb-75Al alloy exhibited the best corrosion resistance among all alloys studied, whose corrosion rates are 1.6–2.2 orders of magnitude lower than those of pure-Nb (depending on temperature). An exclusive NbO₂ layer was formed on pure Nb, while heterophasic scales were observed on Nb-Al alloys whose compositions and amounts strongly depended on Al content and temperature. The scales formed on Nb-12.5Al consisted of mostly NbO₂ and minor amounts of Nb₂O₅, NbS2, and -Al₂O₃, while the scales formed on Nb-25Al consisted of mostly Nb₂O₅ and some -Al₂O₃. The scales formed on Nb-75Al consisted of mostly -Al₂O₃ and Nb₃S₄ atT 900°C, and mostly -Al₂O₃ , Nb₃S₄ and some AlNbO₄ at 1000°C. The formation of -Al₂O₃ and Nb₃S₄ resulted in a significant reduction of the corrosion rates.     

Corrosion of Al-Sn-Bi alloys in alcohol at high temperatures. Part I: Effects of the metallurgical structure of the alloys and the metal salt additions to alcohol

Corrosion of free machining Al alloys that contain Sn and Bi was investigated at 391-415 K in 2-(2-(2-methoxyethoxy)ethoxy)ethanol (MEEE) and 2-(2-(2-butoxyethoxy)ethoxy)ethanol (BEEE) with/without SnCl₂, Sn(OC₂H₅)₄, FeCl₃, and CuCl₂. The Al-Sn-Bi alloy displayed severe pitting corrosion in MEEE similar to the Al-Sn alloy in BEEE at 415 K, and Sn and Sn/Bi were enriched on the surface of pits. Immersion tests of pure Al in MEEE containing Sn/Cu-salts at 415 K also showed severe corrosion and the deposition of metallic Sn and Cu on the surface. The corrosion mechanisms are discussed in terms of the electro-catalytic activity of the Sn enriched on the surface.     

Designing for the cerium-based conversion coating with excellent corrosion resistance on Mg–4Y–2Al magnesium alloy

The cerium salt chemical conversion baths containing KMnO₄ are applied to prepare protective coatings on the WA42 alloy surface, and the effect of the concentration of KMnO₄ on the microstructure and corrosion properties of the coatings is investigated by scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical tests. The results indicate that with the addition of KMnO₄ to the conversion bath, the microstructure of the coating is more uniform and denser, and the coating with the KMnO₄ concentration of 4 g/L (4M coating) has the most uniform microstructure with the least microcracks. The 4M coating exhibits a two-layered structure, and it is mainly composed of MgO, Mg(OH)₂, CeO₂, Ce₂O₃, Ce(OH)₃, MnO, and MnO₂. In addition, as the KMnO₄ concentration increases from 0 to 6 g/L, the I_corr of the coatings in 3.5% NaCl solution decreases first and then increases, and the 4M coating shows the best corrosion resistance, which should attribute to the uniform and dense microstructure.     

Phosphate-permanganate conversion coatings on the AZ81 magnesium alloy: SEM, EIS and XPS studies

Conversion coatings on the magnesium alloy AZ81 were prepared using the phosphate-permanganate baths differing in composition. The corrosion behavior of the coated and uncoated alloys has been investigated by electrochemical impedance spectroscopy (EIS) and linear polarization methods. The choice of proper electric equivalent circuit (EEC) is discussed. The effect of temperature, bath composition and time of conversion as well as etching in acids before application on the corrosion resistance of the coated alloy has been evaluated. The best corrosion resistance was obtained for the samples coated in the bath containing 25 g KMnO₄, 150 g Na₂HPO₄ and 50 ml H₃PO₄ in 1 dcm³, applied at 80 °C. Differences in the morphology and composition of coated surfaces were investigated by the scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques and correlated with the corrosion resistance of the samples.