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The conversion coating was formed by dipping AA6061 in a fluorotitanate/zirconate acid and amino trimethylene phosphonic acid (ATMP) solution at room temperature. The formation process and the anti-corrosion performance of the conversion coating were investigated using electrochemical test and salt spray test (SST), respectively. The electrochemical test shows that the Zr/Ti and ATMP coating improves the corrosion resistance of AA6061 as good as the chromate (VI) coating. But the results of SST show that the corrosion resistance of Zr/Ti and ATMP coating is not as good as the chromate (VI) coating. The corrosion area is less than 2% after 72 h. 相似文献
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为探究转化液主盐酸根在成膜过程中的重要作用,采用扫描电子显微镜、能谱仪、x射线光电子谱仪结合电化学测试对两种常见酸根对应镨盐在镁合金表面形成转化膜后的形貌、成分、元素化学状态以及耐腐蚀性能进行比较,并基于酸根离子在水溶液中的反应过程分析其对转化膜成分及性能的作用机制.结果表明,以PrCl3作为主盐比以Pr(NO3)3作为主盐形成的化学转化膜更加致密;且前者受基体成分的影响较小,形成膜层的Pr、O含量(质量分数)明显高于后者;前者的耐腐蚀性能优于后者.酸根离子对转化膜成分及性能的影响主要体现在镨盐电离后在转化液中形成的相应稀酸与基体合金的作用机制及其对转化膜形成过程的影响. 相似文献
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Corrosion protection of magnesium alloys by cerium, zirconium and niobium-based conversion coatings 总被引:1,自引:0,他引:1
Hélène Ardelean 《Corrosion Science》2008,50(7):1907-1918
A new Ce, Zr and Nb-based conversion coating was designed for AZ91 and AM50 magnesium alloys. The corrosion protection provided by this coating was evaluated by electrochemical measurements (polarization curves, electrochemical impedance spectroscopy) in Na2SO4 electrolyte, and accelerated atmospheric corrosion tests (humid, SO2 polluted air, and salt spray). Its chemical composition was characterized by X-ray photoelectron spectroscopy (XPS). Electrochemical measurements showed that Mg alloys treated during 24 h in the Ce-Zr-Nb conversion bath exhibit: (i) increased corrosion potential, (ii) decreased corrosion and anodic dissolution current densities, and (iii) increased polarization and charge transfer resistances. The accelerated corrosion tests revealed excellent atmospheric corrosion resistance for all Ce-Zr-Nb-treated samples, with or without an additional layer of epoxy-polyamide resin lacquer or paint. XPS analysis showed that the coating includes CeO2, Ce2O3, ZrO2, Nb2O5, MgO, and MgF2 as main components. No significant modification of the chemical composition was observed after cathodic and anodic polarization in Na2SO4. This new coating provides improved corrosion resistance, and excellent paint adhesion. It offers an alternative to the chromate conversion coating for magnesium alloys. 相似文献
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Three molybdate-based conversion coatings on electroplated zinc have been prepared and the composition, morphology, and structure of these coatings are measured by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and X-ray diffraction (XRD), respectively. It was found that these coatings with ‘meshwork’ surface were complex coatings composed of multiple compounds. Molybdenum species were present in the conversion coating as Mo (VI) and Mo (IV) compounds. The results of neutral salt spray test showed that molybdate-based conversion coatings with the addition of H3PO4, SiO2 and TiOSO4 in the passivation baths possess higher corrosion resistance compared with chromate conversion coatings, which was due to the compactness and anti-corrosion essence of the conversion coating. 相似文献
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Nguyen Van Phuong Basit Raza Fazal Sungmo Moon 《Metals and Materials International》2017,23(1):106-114
Electrophoretic painting (E-paint) was prepared on AZ31 Mg alloy samples pretreated in cerium conversion coating (CeCC) solutions with various ratios of ethanol and water mixture and its characteristics, adhesion and corrosion resistance were investigated. It was found that CeCC formed on AZ31 Mg alloy in a CeCC solution without ethanol was partly cracked structure and mainly consisted of Mg(OH)2/MgO, which exhibited weak adhesion with E-painting layer after water immersion test, and low corrosion resistance, as indicated by rapid formation of blisters and paint delamination during salt spray test. The addition of ethanol promoted the growth of a fine nano-crystalline CeO2 layer over the entire substrate surface. The E-paint on AZ31 pretreated in the CeCC solutions with addition of ethanol showed also improved corrosion resistance, as represented by the delayed time for paint delamination and blister formation. The E-paint layers on the CeCC layers formed in solutions containing 50–80 vol% ethanol showed stronger adhesion and better corrosion resistance than those formed on the samples treated in a non-ethanol containing CeCC solution. 相似文献
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Vanadium films were prepared on zinc surfaces by using a solution containing vanadate. Corrosion protection properties of
vanadium-treated (V-treated), chromium-treated (Cr-treated), and untreated zinc surfaces in contact with a 3.5 wt.% NaCl solution
were studied using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and neutral salt spray (NSS)
tests. According to these results, the V-treated layer significantly improved the corrosion resistance of zinc surfaces. In
comparison with the Cr-treated layer, the V-treated layer exhibited a better corrosion resistance. The composition of the
V-treated layer was studied using X-ray photoelectron spectroscopy (XPS). XPS measurements indicated that the vanadium layer
formed on zinc surfaces and the vanadium-rich coating was a hydrated oxide with a composition of V2O5, VO2, and its hydrates such as V2O5·nH2O and VO(OH)2. 相似文献
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The corrosion resistance of vanadium-based conversion coatings on electro-galvanised steel (EG) was examined in terms of the different valence species V5+ and V4+ as the raw material in the treatment solution. The effects of mixing phosphoric acid with the vanadium-based conversion coating have also been investigated. Corrosion performance was tested by neutral salt spray test and the mechanism of corrosion resistance was analysed by electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. It was found that conversion coatings formed from V5+ or V4+ did not clearly show different corrosion behaviour, but that the addition of phosphoric acid to the solution including V5+ improved corrosion protection. These results indicate that mixing phosphoric acid lowers the pH of the solution and improves corrosion resistance. The role of phosphoric acid is also explained by the formation of hydrogen bonds at the interface between the vanadium species and EG substrate. 相似文献
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Mei-rong Yuan 《Surface & coatings technology》2010,204(8):1229-118
Passivation treatment by sodium silicate solution is considered as an alternative to chromium chemical conversion treatment to improve the corrosion resistance of hot-dip galvanized (HDG) steels. In this paper, a transparent silicate coating was formed on the surface of HDG steel by immersing in sodium silicate solution with SiO2:Na2O molar ratio in the range from 1.00 to 4.00. The parameter about the SiO2:Na2O molar ratio of silicate solution has been discussed using corrosion resistance and surface morphology. Tafel polarization, electrochemical impedance spectroscopy (EIS) measurements and neutral salt spray (NSS) test show that silicate coatings increase the corrosion resistance of HDG steels. From the results obtained, it is deduced that the optimum SiO2:Na2O molar ratio is 3.50. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction analysis (XRD), and reflectance absorption infrared spectroscopy (RA-IR) show that there are no obvious differences of the chemical composition and structure in various silicate coatings. The silicate coatings mainly consist of zinc oxides/hydroxides, zinc silicate and SiO2. However, atomic force microscopy (AFM) images reveal that the surface of silicate coatings with a molar ratio of 3.50 is more compact and uniform than other silicate coatings. 相似文献
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An organic-magnesium complex conversion (OMCC) coating on AZ91D magnesium alloy was obtained by treating in a solution containing organic compounds. SEM, FESEM and XPS were used to examine the surface morphology, thickness and structure of the conversion coatings. The results show that the continuous and uniform conversion coating is deposited on AZ91D alloy and the main component of the coatings is organic compound containing benzene ring, which forms a chemical bond with magnesium. The polarization measurement and salt spray test show that the corrosion resistance of the conversion coating is much higher than that of traditional chromate conversion coating. 相似文献
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方信贤 《腐蚀科学与防护技术》2010,22(2):109-112
研究了硫酸铜加入量对化学镀Ni-Cu-P合金的镀层成分、组织及热稳定性影响,用中性盐雾实验和在20%H2SO4+20 g/LAl2O3溶液中的冲刷腐蚀实验研究了Ni-P与Ni-Cu-P合金的耐蚀性和耐冲刷腐蚀性能.结果表明,Ni-Cu-P合金镀层具有比Ni-P合金镀层更好的热稳定性、耐蚀性和耐冲刷腐蚀性能. 相似文献
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Electroless Ni? P? Al2O3 composite coatings have been synthesized on mild steel shafts using surfactant cetyltrimethyle ammonium bromide (CTAB) as dispersant. The effects of the surfactant on the alumina dispersion, weight fraction in coatings, and corrosion resistance of the composite coatings under salt spray test were investigated. Results showed that alumina dispersion was improved, whereas weight fraction was decreased, with the increasing concentration of the dispersant CTAB. The corrosion resistance of the composite coatings was found to increase with the increase in CTAB concentration up to a certain optimum of 20 mg/L, beyond which a decreasing trend of corrosion resistance was observed under salt spray test. Compared with Ni? P coating, all the Ni? P? Al2O3 composite coatings showed improved corrosion‐resistant properties. 相似文献
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NiCoCrAlYSiB coatings were deposited by arc ion plating (AIP) and annealed/pre-oxidised under various conditions. The corrosion behaviour of as-deposited and annealed/pre-oxidised coatings was studied by salt spray testing in a neutral mist of 5 wt% NaCl at 35 °C for 200 h. The results showed that the as-deposited NiCoCrAlYSiB coating behaved poorly while the annealed and pre-oxidised ones performed much better in salt spray tests. The dense microstructure in annealed coatings and formation of α-Al2O3 scales on the surface during pre-oxidation improved the corrosion resistance in salt spray test. The corrosion process was investigated from the aspects of corrosion products, and its electrochemical mechanism was proposed as well. 相似文献
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镀锌板硅烷-硝酸锆复合转化膜的性能与表征 总被引:2,自引:2,他引:0
目的获得一种防腐性能优越的转化膜。方法将KH560和KH791两种硅烷复合后水解,添加硝酸锆,得到KH560-KH791-硝酸锆复合钝化液,采用该钝化液对镀锌钢板进行钝化处理,通过盐水浸泡实验、中性盐雾试验和附着力测试,与添加硝酸锆前的转化膜进行性能对比。结果盐水浸泡和中性盐雾腐蚀72 h的实验中,添加硝酸锆后的转化膜性能都明显优于添加前,二者的附着力测试均能达到一级。结论加入的硝酸锆填充了膜层空隙,更加有效地阻挡了腐蚀介质的渗透,使得钝化膜的防腐性能提高。 相似文献
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采用喷涂工艺在烧结钕铁硼磁体表面制备了不同纳米 CeO2 掺杂量的 CeO2 / Zn-Al 复合涂层。 利用扫描电子显微镜、显微硬度仪、盐雾试验箱和电化学工作站对 CeO2 / Zn-Al 复合涂层的微观结构、力学性能及耐腐蚀性能进行表征分析。 结果表明:CeO2 纳米颗粒较均匀弥散分布于 Zn-Al 涂层中,不仅能够增加 Zn-Al 涂层的硬度,而且可以提高 Zn-Al 涂层的屏蔽性能,CeO2 / Zn-Al 复合涂层耐中性盐雾试验能力高达 720 h。 添加的 CeO2 颗粒能够隔绝 Zn-Al 涂层中的锌铝薄片之间的直接接触,起到绝缘作用,延长了腐蚀介质渗入钕铁硼基体的腐蚀通道。 相似文献
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A tannic acid based conversion coating was formed on AZ91D magnesium alloy through a solution containing C76H52O46 (tannic acid), NH4VO3, K2ZrF6 and H3PO4. The growth process and corrosion resistance of the conversion coating were investigated by SEM, FESEM, XPS, IR, potentiodynamic polarization and EIS test. The results showed that the main components of the coatings were penta-hydroxy benzamide–magnesium complex, Al2O3 and MgF2. Zr(HPO4)2·H2O(α-ZrP) was first formed in the time interval of 70 s–120 s, which acted as catalyst to activate the main reaction of gallic acid being oxidized into the penta-hydroxy benzamide–magnesium complex, as well as the formation of MgF2 and Al2O3, which took place in the time interval of 120 s to 600 s. The thickness of coating treated for 300 s and 600 s was 1.1 μm and 1.6 μm, respectively. Polarization measurement and EIS test in 3 wt.% NaCl solution indicated that the conversion coating treated for about 300–600 s shows good corrosion resistance while an excess time treatment (720 s) induces the coating surface coarse and uneven, leading to the reduction of corrosion resistance of the conversion coating. 相似文献