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.     

基于正交实验优化不锈钢表面纳米孔结构制备工艺

目的通过正交实验优化不锈钢表面纳米孔制备工艺。方法通过田口实验方法设计正交试验优化工艺。采用含有氯化钠和硫脲的硝酸溶液阳极氧化制备纳米孔,在含有氯化钠、盐酸和硫酸的水溶液中进行扩孔处理。通过扫描电子显微镜、能谱仪对表面处理后的试样表面形貌和元素进行分析,应用软件统计SEM图片孔隙率,并将孔隙率作为响应指标,利用极差分析和方差分析研究阳极氧化工艺和扩孔时间对表面形貌及孔隙率的影响,并优化工艺参数。结果 SEM照片和5个水平的均值表明,硝酸浓度的提高有利于提高孔隙率,较高的硫脲浓度有利于形成均匀有序的纳米孔结构,氯化钠浓度、氧化时间、氧化电压和扩孔时间对表面形貌和孔隙率影响不明显。元素分析表明,纳米孔的材料仍然是不锈钢,而不是金属氧化物。正交实验优化的工艺参数是:硝酸的体积浓度为90 mL/L,硫脲的质量浓度为3.5 g/L,氯化钠的质量浓度为20 g/L,氧化时间为120 s,氧化电压为5.0 V,扩孔时间为50 s。结论通过实验验证,优化后的工艺能够制备出表面较平整、孔隙率较高的纳米孔结构。     

6063铝合金阳极氧化过程中麻点问题分析

通过表面形态和显微组织观察,采用扫描电镜(SEM)、能谱(EDS)等手段分析了6063铝型材在阳极氧化过程中出现麻点的原因.结果表明,麻点实质为点腐蚀,是由于合金中游离态Si、金属间化合物、过量Zn等导致的择优腐蚀,以及Cl-加速了铝合金的活性溶解.     

Environmental friendly anodizing of AZ91D magnesium alloy in alkaline borate-benzoate electrolyte

A kind of environmental friendly anodizing routine for AZ91D magnesium alloy, based on an alkaline borate-sodium benzoate electrolyte (NaBz) was studied. The effect of NaBz on the properties of the anodized film was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), respectively. The results showed that the anodizing process, surface morphology, thickness, phase structure and corrosion resistance of the anodized film were strongly dependent on the concentration of NaBz. In the presence of adequate NaBz, a thick, compact and smoothing anodized film with excellent corrosion resistance was produced. Moreover, the forming mechanism of the anodized film in the presence of NaBz additive was also approached, which was a suppression of arc discharge process by the adsorption of Bz⁻ on the surface of magnesium alloy substrate.     

An investigation into the mechanical and tribological properties of plasma electrolytic oxidation and hard-anodized coatings on 6082 aluminum alloy

A ceramic coating on AA6082 aluminum alloy prepared by plasma electrolytic oxidation (PEO) has been studied and compared against a sulphuric acid hard-anodized coating on the same alloy. Surface morphology and microstructures of the coatings have been examined by scanning electron microscopy. X-ray diffraction is used to determine the phase composition of the coatings. The adhesion strength of the coatings has been evaluated using a scratch test method. The coating's mechanical properties such elastic modulus and hardness data have been generated using a dynamic ultra-microhardness tester. Sliding wear tests with different loading rates are performed on the coatings in order to assess their wear resistance. Test results show that the PEO treated samples exhibit significantly better mechanical properties compared to hard anodized samples. The elastic modulus and hardness of the PEO coating are 2-3 times greater than of the hard anodized coating and subsequently, an improved wear resistance of the PEO coating has been achieved. The mechanical properties of the coatings and their relations to their tribological performance are discussed.     

聚苯胺掺杂对2A12铝合金阳极氧化复合膜耐蚀性的影响

目前,国内尚未见有关铝合金表面聚苯胺-阳极氧化复合膜的研究报道.采用电化学共沉积技术在2A12铝合金表面制备了非导电聚苯胺-阳极氧化复合膜、导电聚苯胺-阳极氧化复合膜,利用傅立叶红外光谱(FTIR)、能谱分析、极化曲线、交流阻抗及中性盐雾试验对膜层的性能进行了研究.结果表明:2种复合膜均能明显提高2A12铝合金的自腐蚀...     

Fretting fatigue behaviour of hard anodizing coated 2014‐T6 aluminium alloy with dissimilar mating materials under plane bending loading

The effect of hard anodizing coated 2014‐T6 aluminium alloy test samples with dissimilar mating materials on fretting fatigue was investigated. Fretting fatigue configuration involved bridge‐type pads on the flat specimen. Bridge‐type pads were made of AISI 4140 steel. All the fretting fatigue tests were conducted under plane bending loading with a stress ratio of R=?1. Coated and uncoated specimens were compared for microhardness, surface roughness, tangential force. The specimens were tested under both plain fatigue and fretting fatigue loading at ambient temperature. Micrographs obtained from scanning electron microscope showed that hard anodizing coating had tiny cracks through the thickness of the anodized layer. The hardness of hard anodized coating was higher than that of uncoated specimens and they also exhibited lower tangential force. However, the fretted region of the hard anodizing coated specimens was rougher than that of uncoated samples and despite lower tangential forces, fatigue lives of hard anodizing coated samples were inferior to those of uncoated samples. As the hard anodizing coating had pre‐existing tiny cracks and tension residual stress, cracks propagated from the hard anodizing coating through the interface into the substrate. We conclude that these may be the main reasons for inferior fretting fatigue lives compared with uncoated samples.     

表面活性剂十二烷基磺酸钠对镁合金阳极氧化的影响

在含柠檬酸钠的碱性硅硼体系中对AZ91D镁合金进行电化学阳极氧化成膜处理,通过记录阳极氧化电压随时间的变化以及扫描电镜、能谱仪和电化学测试等方法考察了阴离子型表面活性剂十二烷基磺酸钠(SDS)对镁合金阳极氧化过程和氧化膜性能的影响。结果表明,在阳极氧化过程中,十二烷基磺酸根离子被吸附到镁合金电极表面,增加了表面膜层电阻,提高了阳极氧化电压,使得阳极氧化膜层更致密、厚度分布更均匀,减少了表面微气孔。当SDS含量为0.2~0.4 g/L时,所得阳极氧化膜具有最大的电荷传递电阻和膜电阻,对镁合金具有最好的腐蚀防护性能。     

乙二胺四乙酸对镁合金阳极氧化膜的影响

将AZ31镁合金在NaOH、Na2SiO3和Na2B4O7的电解液中进行阳极氧化,考察了乙二胺四乙酸添加剂对阳极氧化膜性能的影响。用扫描电镜观察阳极氧化膜形貌,用X-射线衍射和自带能谱仪对膜层的相组织和元素含量进行分析,用交流阻抗测试氧化膜的耐蚀性能。结果表明,氧化膜主要由Mg O组成,膜层中出现了乙二胺四乙酸的特征元素C和N,Mg Si O3的衍射峰受到抑制。阳极氧化过程中的起弧电压随乙二胺四乙酸含量的增加呈上升的变化趋势。随着乙二胺四乙酸含量的增加,膜层耐蚀性先提高后降低。乙二胺四乙酸质量浓度为7.5 g/L时氧化膜具有最大的阻抗,最优的耐蚀性能。