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Caruline de S. C. Machado Rafael E. Klumpp Victor H. Ayusso Uyime Donatus Mariana X. Milagre João V. de S. Araujo Glauson A. F. Machado I. Costa 《Surface and interface analysis : SIA》2019,51(12):1231-1239
In this work, the effect of eight types of surface treatments on the corrosion resistance of friction stir welded samples of an AA2198-T8 Al-Cu-Li alloy were tested and compared in an attempt to find suitable alternatives to toxic and carcinogenic hexavalent chromium treatments. All the samples were anodized and subjected to different post-anodizing treatments. The post-anodizing treatments were (1) hydrothermal treatment in Ce (NO3)3 6H2O solution; (2) hydrothermal treatment in Ce (NO3)3 6H2O solution with H2O2; (3) hydrothermal treatment in boiling water; (4) hexavalent chromium conversion coating; and (5) immersion in BTSE (bis-1,2-(triethoxysilyl) ethane. The corrosion resistance of the treated samples was evaluated by immersion tests in sodium chloride solution (0.1 mol L−1 NaCl) and electrochemical impedance spectroscopy (EIS) of the friction stir weldment. The results showed that among the alternative treatments, the Ce-containing solutions presented the best corrosion resistance, especially when used without peroxide. 相似文献
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研究了不同Cr含量的Fe-Cr合金在H2SO4溶液体系中的摩擦腐蚀过程,重点了载荷,摩擦速度,Cr含量及H2SO4溶液浓度对摩擦电流密度的影响。结果表明:当摩擦仅作用在金属部分表面时,在钝化电位区,外加载荷和摩擦速度对摩擦电流密度有较大的影响。 相似文献
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铁铬合金摩擦破损微电偶的形成及作用 总被引:5,自引:1,他引:5
本文分析,研究了1Cr18合金材料在0.2mol.L^1H2SO4溶液中的摩擦腐2蚀过程中产生微电偶腐蚀的可能性及原因,并研究了微电偶对摩擦电化学行为的影响,研究结果表明:由于摩擦过程造成材料表面的电化学不均一性是产生微电偶作用的真正原因。未摩擦表面与摩擦表面的面积比显著地影响了摩擦电偶电位和摩擦电偶电流的大小。 相似文献
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Jean-Louis Pouchou Denis Boivin Yves Renollet Christophe Gallais 《Mikrochimica acta》2004,145(1-4):171-176
A dedicated procedure has been carried out to enable EBSD orientation mapping of large-fields, by combining beam scanning and stage control in order to acquire a patchwork of overlapping areas, and by using specially developed software to reconstruct the EBSD file of the large-field from the individual files. This procedure has been successfully used to study the microstructure of a friction stir welding nugget in an aluminium alloy. 相似文献
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A combined stir bar coated with poly (dimethysiloxane)-beta-cyclodextrin (PDMS-beta-CD) on single side has been prepared for the first time by sol-gel method and was coupled with ultrasonic assisted extraction (UAE) for the determination of some brominated flame-retardant compounds (BFRs) in soil and dust samples by high performance liquid chromatography (HPLC). Four different kinds of coatings including PDMS-beta-CD, PDMS, carbowax (CW)-PDMS-poly (vinyl alcohol) (PVA) and PDMS-PVA were evaluated for stir bar sorptive extraction of BFRs by orthogonal experiment design. The experimental results reveal that the PDMS-beta-CD combined stir bar exhibited the best extraction efficiency for the target analytes. The reproducibility for the preparation of PDMS-beta-CD combined stir bar ranged from 1.3% to 15.7% in one batch, and 7.2% to 15.1% among batches. Extraction time, desorption solvent, concentration of methanol and NaCl in the matrix, pH, temperature and stirring speed were optimized. The combined stir bar can avoid direct friction of the coating with the bottom of the vessel, and could be used for more than 100 times. Linearity (>0.993), repeatability (<10.5%), reproducibility (<16.5%), recovery (56-118%) and detection limits (2.9-4.2 microg L(-1)) were proper to determine the seven BFRs. The developed method was applied to the determination of BFRs in soil and dust with satisfactory results. 相似文献
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Rampulla DM Mancinelli CM Brunell IF Gellman AJ 《Langmuir : the ACS journal of surfaces and colloids》2005,21(10):4547-4553
The origins of the tribological properties and corrosion resistance of amorphous and quasicrystalline approximant alloys have been studied by comparing their properties in thin Al-Cu-Fe alloy films with compositions lying near the quasicrystalline region of the ternary compositional phase diagram. Six sputtered thin films of an Al-Cu-Fe alloy were studied using X-ray diffraction, X-ray photoemission spectroscopy (XPS), and an in situ ultrahigh vacuum (UHV) tribometer. The films were annealed in UHV to induce the formation of orthorhombic, rhombohedral, and amorphous bulk structures. The properties of these thin films were then determined in the same UHV apparatus without exposing the films to air. The rates of surface oxidation by H2O and O2 were measured using XPS. Although the oxidation rates and oxide thicknesses were dependent on the oxidant, they were not sensitive to the structures of the films. Friction was measured between identical samples in sliding contact. The friction coefficients (micros = 0.36 +/- 0.11 to 0.56 +/- 0.08) were comparable to those observed in other experiments using quasicrystals and approximants in UHV; however, there was no strong correlation between the friction coefficients and either the film structure or the degree of surface oxidation. These results suggest that the tribological and corrosion resistance properties of these quasicrystalline approximant alloys are not directly connected to crystalline structure. 相似文献
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The technique of calculation of a feeding zone for a single screw extruder is developed taking into account the nonisothermal
process and the actual boundary geometric conditions and speed conditions (the screw is rotated, the cylinder is fixed). An
analysis of the influence of the screw geometry was performed and also of an effect of a ratio of friction coefficients of
the processed material on the cylinder and worm, on a change in pressure and temperature of the processed material along the
length of the feeding zone. 相似文献
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The partial suppression of corrosion of Ag and Cu in concentrated nitric acid solution by a magnetic field of up to 5 T was studied. The corrosion current density of these metals was found to diminish with magnetic field and rotation speed in a rotating disk electrode experiment. The suppression of corrosion is associated with removal of the catalyst HNO(2) from the electrode and passivation of the electrode surface. The Lorentz force was identified as the driving force responsible for the partial suppression of corrosion. A model based on the partial areas associated with active and passive regions on Ag and Cu electrodes is introduced to explain the dependence of the current density on the applied magnetic field. 相似文献
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《Arabian Journal of Chemistry》2020,13(7):6044-6055
The corrosion of AZ91D magnesium alloy has received extensive attention due to the continuous expansion of its application field in recent years. However, the corrosion of AZ91D magnesium alloy in distilled water is relatively few. In this paper, the corrosion behavior of AZ91D magnesium alloy was studied in distilled water by electrochemical tests in combination with weight loss and surface analysis methods. The results indicated that the corrosion rate of AZ91D magnesium alloy increased with the increase of temperature and immersion time. The increase of the corrosion rate of AZ91D magnesium alloy with the increase of immersion time might be attributed to the damage of the structure of corrosion product film by hydrogen evolution, significantly accelerating the anodic process of AZ91D magnesium alloy. It was interesting that, in distilled water, the EIS of AZ91D magnesium alloy excluded an inductive arc in the low frequency region, which indicated that there was no the adsorption and desorption of aggressive ions or the damage and repair of film. The corrosion product film of AZ91D magnesium alloy in distilled water was composed of a compact inner corrosion product film and a loose outer corrosion product film. 相似文献
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S.T. Amancio-Filho J. Roeder J.F. dos Santos 《Polymer Degradation and Stability》2008,93(8):1529-1538
The thermal degradation of polyetherimides joined by friction riveting (FricRiveting) (Amancio Filho ST, Beyer M, Dos Santos JF. Verfahren zum Verbinden eines metallischen Bolzens mit einem Kunststoff-Werkstück - DE 10 2005 056 606 A1. Germany: Deutsches Patent- und Markenamt; 2007) has been investigated for varying rotation speeds. The rotation speed is an important variable to be understood in order to predict thermal degradation during this process. Investigated rotation speeds in the range of 1570-2199 rad/s resulted in high process temperatures (350-475 °C) and heating rates (up to 2 °C/100 rad/s), but only small heating times (<3 s). Thermal degradation was evaluated by gel permeation chromatography, Fourier transform infrared spectroscopy and X-ray computer microtomography. The results indicated that thermal degradation in the PEI polymer was mainly due to chain scission. Moreover, the small level of thermally degraded material (average drops of 10% in molecular weight) showed only a minor dependence on rotation speed. Although high peak temperatures and heating rates were present, the restricted variation and average values of heating time were insufficient to cause strong thermal changes in the joints of the studied rotation speed range. 相似文献
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E. V. Nikitina N. A. Kazakovtseva M. A. Maikov V. B. Malkov E. A. Karfidov A. Yu. Chuikin 《Russian Journal of Electrochemistry》2018,54(9):697-701
The interaction of the monel alloy and its corrosion resistance in a melt of alkali metal carbonates in an oxidizing atmosphere was studied. The selectivity of alloy dissolution and modification of the electrode surface after storage at a constant anode potential were analyzed. The generation and development of local corrosion defects (pit corrosion, intercrystallite corrosion, corrosion cracking) on monel alloy (70% nickel, 28% copper), copper, and nickel electrodes in the molten eutectic of lithium, sodium, and potassium carbonates at a working temperature of 773 K were studied. The anode polarization was accompanied by a change in the state of the electrode surface. 相似文献
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阳极氧化AZ91D镁合金在氯化钠稀溶液中的腐蚀行为 总被引:1,自引:1,他引:0
利用盐雾实验、极化曲线扫描、电化学阻抗谱和电化学噪声技术等电化学研究方法结合扫描电镜表面观测技术对AZ91D镁合金氧化膜在1%(w)氯化钠溶液中的耐蚀性能进行了评价. 结果表明, 氧化前后的镁合金腐蚀行为发生明显改变, 如未封孔的阳极氧化膜耐中性5%氯化钠盐雾试验时间超过200 h; 氧化后的镁合金自腐蚀电位明显正移, 点蚀诱导期延长; 阳极氧化膜的高频阻抗约为裸露镁合金的数千倍, 这些变化证明阳极氧化处理使镁合金获取了十分优异的耐蚀性能. 首次利用分形维数Df的变化规律初步描述氧化后AZ91D镁合金的腐蚀过程. 可以发现随着浸泡时间的延长, Df呈现出初期快速增长, 随后出现波动, 最后稍有降低的变化过程. 这种现象对应于氧化后AZ91D 镁合金在1%氯化钠溶液中腐蚀的三个阶段. 相似文献
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HCl acid was applied to the surface of the self-prepared Cu-Sn-Pb alloy, and the methods of IR-REF, IR-PAS, XRD, SPM, SEM, TEM and pH were employed to study the forming process and the developing speed of the bronze powder-corrosion Cu_2(OH)_3Cl (PC). It is found that the corrosion develops fast in acid environment at room temperature; the corrosion Cu_2(OH)_3Cl with valence Cu~(2+) forms from alloy through the intermediate corrosion CuCl with valence Cu~+; PC is contagious, which can pollute the fresh bronze alloy from the corroded sample by air; when CuCl is oxidized to produce Cu_2(OH)_3Cl, Cu~(2+) cation forms at the same time, and both the oxidizing reactions have zero-order reaction with respect to O_2 in the air; the P1 formation reaction has first-order reaction with respect to Cull; in enormous distilled water Cu_2(OH)_3Cl forms from CuCl through the intermediate product Cu_2O.All the results above are discussed in the present article, and the mechanism of PC formation is studied further. The r 相似文献
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采用析因分析试验及动电位极化曲线、电化学阻抗谱(EIS)等测试方法,研究了海水环境因素中的典型阴离子(Cl-、HCO3-、SO42-交互作用对5083铝合金耐蚀性的影响. 结果表明,三种阴离子中,Cl-、HCO3-对铝合金点蚀起促进作用. Cl-与HCO3-交互作用时,在Cl-浓度一定的情况下,随着HCO3-浓度的增加,5083铝合金耐蚀性呈现出上升→下降→再上升的趋势,在70~90mg•L-1时耐蚀性能明显降低;在HCO3-浓度一定的情况下,Cl-浓度较低时5083铝合金耐蚀性比Cl-浓度较高时差. 在Cl-、HCO3-浓度较低情况下,SO42-具有抑制腐蚀的作用;当Cl-、HCO3-浓度较高时,SO42-抑制腐蚀的作用不明显. 相似文献
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Ishizaki T Masuda Y Sakamoto M 《Langmuir : the ACS journal of surfaces and colloids》2011,27(8):4780-4788
The corrosion resistant performance and durability of the superhydrophobic surface on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution were investigated using electrochemical and contact angle measurements. The durability of the superhydrophobic surface in corrosive 5 wt% NaCl aqueous solution was elucidated. The corrosion resistant performance of the superhydrophobic surface formed on magnesium alloy was estimated by electrochemical impedance spectroscopy (EIS) measurements. The EIS measurements and appropriate equivalent circuit models revealed that the superhydrophobic surface considerably improved the corrosion resistant performance of magnesium alloy AZ31. American Society for Testing and Materials (ASTM) standard D 3359-02 cross cut tape test was performed to investigate the adhesion of the superhydrophobic film to the magnesium alloy surface. The corrosion formation mechanism of the superhydrophobic surface formed on the magnesium alloy was also proposed. 相似文献