镍/纳米二氧化硅纳米复合镀层耐腐蚀性能的研究

制备了纳米氧化硅镍复合镀层材料,并利用静态浸泡法对纯镍镀层和由镀液中不同微粒含量制备的复合镀层样品的耐蚀性能进行了研究,讨论镀液中纳米微粒含量对镀层抗蚀性能的影响。并用扫描电镜观察镀层的表面形貌。     

Fabrication of hydrophobic surface with hierarchical structure on Mg alloy and its corrosion resistance

A hydrotalcite/hydromagnesite conversion coating with hierarchical structure has been fabricated on a Mg alloy substrate by in situ hydrothermal crystallization method. A MgO layer existing between the hydrotalcite/hydromagnesite film and the substrate was formed prior to the hydrotalcite/hydromagnesite film during the crystallization process. After surface treatment with silane coupling agent, the surface of conversion coating changes from hydrophilic to hydrophobic. Scanning electron microscopy (SEM) revealed that the silylated conversion coating with hierarchical structure maintains the original rough surface of which was composed of numerous micro-scale flakes and beautiful flower-like protrusions. Polarization measurements have shown that the hydrophobic conversion coating exhibited a low corrosion current density value of 0.432 μA/cm², which means that the hydrophobic conversion coating can effectively protect Mg alloy from corrosion. Electrochemical impedance spectroscopy (EIS) showed that the impedance of the hydrophobic conversion coating was 9000 Ω. It means that the coating served as a passive layer with high charge transfer resistance.     

Fabrication of Ni-W-B4C composite coatings and evaluation of its micro-hardness and corrosion resistance properties

Boron carbide (B₄C) particles were embedded in nickel-tungsten (Ni-W) coatings by pulse current electrodeposition technique. Physical properties of the composite coatings were studied by XRD, SEM, EDS and Vickers micro-hardness instrument. Corrosion protection of the deposited films was investigated utilizing potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS). Results exhibited that the addition of B₄C nanoparticles into the Ni-W alloy can significantly improve the surface morphology and the micro-hardness of the composite coatings. The corrosion resistance of Ni-W-B₄C nanocomposite is much better than Ni-W alloy deposit, especially when the concentration of B₄C nanoparticles is 2?g/L in plating bath, the obtained Ni-W-B₄C composite coating has the best surface morphology, the highest micro-hardness and the excellent corrosion resistance.     

Phase and structure formation mechanisms of SHS synthesized composite coatings

High performance composite coatings were synthesized by self-propagation high-temperature synthesis followed by gravitational-separation process based on thermite reaction. The phase, structure and composition of generated composite coatings were investigated, and formation mechanism was studied by thermodynamic analysis. Results showed that phase composition of Al-Fe₂O₃ reaction system consisted of Al₂O₃, Fe and FeAl₂O₄. In Al-Fe₂O₃/Al-Cr₂O₃ composite reaction system, Fe-Cr alloy was formed and FeAl₂O₄ phase disappeared, which could improve the corrosion resistance of composite coatings. Furthermore, the addition of SiO₂ in SHS reaction favored the formation of low-melting point phase Al₂O₃·SiO₂, which filled into voids of Al₂O₃ dendrites and reduced the porosity of composite coatings, thus improving their strength and densification level. Moreover, the generated transition structure in different reaction systems could buffer the residual stress to promote the binding between the composite coating and steel pipe.     

Efficient one-step fabrication of superhydrophobic nano-TiO2/TMPSi ceramic composite coating with enhanced corrosion resistance on 316L

TiO₂ Nanoparticle/Trimethoxy(propyl)silane (TMPSi) ceramic composite coating was deposited on 316L steel using a one-step electrophoretic deposition (EPD) method. Silane coupling agent (TMPSi) was added to the EPD bath in different concentrations (from 0.5 to 15 vol %) to decrease the surface energy of the deposited coating. TiO₂ coating is hydrophilic whereas by adding varying concentrations of TMPSi, the obtained nanocomposite coating showed much better hydrophobicity. Surface wettability was measured by water contact angle (WCA) and sliding angle (SA) tests. Moreover, the effect of TMPSi concentration was determined by comparing the WCA and SA values. Surface morphology was studied through Field Emission Scanning Electron Microscopy (FESEM), and the presence of micro/nano meter roughness on the surface was confirmed. The distribution of elements were investigated by EDS analysis in which their uniform dispersion was observed. Corrosion behavior of 316L samples before and after the coating process was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests in 3.5 wt % NaCl solution. The polarization curve proved that the superhydrophobic ceramic nanocomposite coatings (WCA = 168° and SA = 3.1°) were able to decrease the corrosion rate of bare 316L (from 12.180 to 5.621 (μm per year)).     

Evaluation of the corrosion resistance of phosphate coatings obtained by anodic electrochemical treatment

The corrosion resistance of phosphate coating obtained by anodic electrochemical treatment at 4–6 mA/cm² is addressed in this paper. The corrosion performance of these coatings is also compared with the coatings obtained by chemical treatment. The regenerated phosphoric acid under the influence of anodic current causes a large variation in morphological features of the coatings. Immersion and salt spray tests indicate the ability of these coatings to act as a barrier film on mild steel. Polarization and electrochemical impedance spectroscopic (EIS) studies indicate that the corrosion resistance of phosphate coatings obtained by anodic treatment decreases with increase in current density employed for deposition. In spite of their higher coating weight, the corrosion resistance of phosphate coatings obtained by anodic treatment is inferior to those obtained by chemical treatment. The porosity or discontinuities created due to the dissolution of the coating under the influence of anodic current are considered responsible for the inferior corrosion resistance of these coatings. The study concludes that anodic treatment has only a limited scope for preparing phosphate coatings with improved corrosion resistance.     

复合硅烷/锌涂层耐腐蚀性能的研究

通过电导率监视仪对硅烷的水解过程进行监控,确定了KH560的水解时间为3h,含不同质量分数鳞片锌粉的硅烷/锌复合液的水解时间为12h。将硅烷/锌水解液涂覆到低碳钢表面,制备了复合硅烷/锌涂层。通过盐雾试验、极化曲线和交流阻抗谱研究了不同锌粉含量的硅烷/锌复合涂层的耐蚀性能,通过扫描电镜观察了涂层的截面形貌,探讨了硅烷/锌复合涂层的耐蚀机理。结果表明,复合硅烷/锌涂层的耐蚀性能随着锌粉含量的增加而提高,鳞片锌粉的最大添加量为45%。此含量下的复合硅烷/锌涂层的耐蚀性能最好,中性盐雾时间达576h,是纯硅烷涂层的12倍。在此硅烷/锌复合涂层中,鳞片锌粉以平行叠加的方式组成致密的网状结构,从而延长了腐蚀性介质到达金属基材的时间,使涂层的耐蚀性能得到明显提高。     

Improvements on corrosion behaviours of MgO-spinel composite refractories by addition of ZrSiO4

Corrosion behaviours of MgO-spinel-ZrSiO₄ compositions were investigated. The influence of corrosion resistance based on the microstructural changes occurred due to the solubilities of constituents in corroded regions was examined using SEM/EDX analysis. The following observations were determined by microstructural characterisation performed at the interface of clinker-refractory: (i) the formation of ZrO₂ and Mg₂SiO₄ phases among MgO grains after sintering, (ii) the formation of CaZrO₃ phase during penetration, (iii) prevention of penetration by new phases formed making a barrier effect against clinker with an improvement in densification, and (iv) the decrease in the amount of CaO and the increase in the quantity of MgO using EDX analysis made moving from clinker towards refractory. The addition of ZrSiO₄ reduced the values of penetration and spreading areas of the corroded regions of composite refractories and improved the corrosion resistance significantly, leading to a long service life of MgO-spinel-zircon based refractories for industrial applications.     

Preparation and corrosion resistance of nonstoichiometric lanthanum zirconate coatings

Lanthanum zirconate is a promising thermal barrier coating material owing to its excellent thermophysical properties and La plays the key role in its corrosion resistance. Here, an amorphous precursor is used as raw feedstock material so as to synthesize lanthanum zirconate coatings with tailorable composition by atmospheric plasma spray (APS). Three lanthanum zirconate coatings of La_1.7Zr_2.3O_7.15, La_2.0Zr_2.0O_7.0 and La_2.3Zr_1.7O_6.85 are fabricated. Furthermore, the corrosion resistance of the as-sprayed coatings against CaO-MgO-Al₂O₃-SiO₂ at 1250℃ is investigated. The increased La content promotes the formation of a sealing layer of the crystalline Ca₂La₈(SiO₄)₆O₂ apatite, which slows down the penetration of molten CaO-MgO-Al₂O₃-SiO₂. Therefore, the infiltration rate of the La_2.3Zr_1.7O_6.85 coating decreased up to 42.6 % compared with the other two coatings. This work develops a feasible preparation strategy to control the La composition for the improved corrosion resistance, which is expected to guide the future coating design and synthesis for the materials with big composition changes during the APS process.     

Improvement of corrosion resistance of magnesium metal by rare earth elements

Mg metal containing rare earth metals (REs) can be electrowon directly by molten salt electrolysis. The clarification of the optimum RE content in Mg is necessary to fix the electrolytic conditions in the direct electrowinning of Mg with RE. From this point of view, effect of RE addition in Mg metal on its corrosion property was studied in detail in this study. The specimen was prepared by adding La, Nd, or Ce in melted Mg metal, and its corrosion resistance was examined by an immersion test in 3 mass%-NaCl solution at room temperature. The corrosion resistance of Mg was improved greatly by adding a small amount of RE, whereas the excess addition of RE deteriorated the corrosion resistance. The optimum RE content was about 0.5 mass%. In this study, the corrosion property of Mg with an artificial surface oxide layer was also studied to clarify the effect of surface oxide. The corrosion resistance of Mg was particularly strengthened by conversion coating in a solution including La(NO₃)₃, Nd(NO₃)₃, or Ce(NO₃)₃, with Mg(NO₃)₂. This result suggests that the surface oxide film consisting of both Mg and RE gives ideal corrosion resistance to Mg metal. Mg metal with conversion coating including RE should also be of use as a corrosion-resistant material.     

Synthesis and characterization of Ni-W/TiN nanocomposite coating with enhanced wear and corrosion resistance deposited by pulse electrodeposition

To enhance mechanical properties and anti-corrosion capability of Ni-W alloy further, Ni-W/TiN nanocomposite coating has been co-deposited via pulse current co-deposition in this work. The effects of TiN nanoparticles and operating parameters on the structure and properties of the deposited coating were examined. It illustrated that the nanocomposite coatings are uniform, dense and crack-free, exhibiting dome-like or hill-valley like structure. The particles were homogeneously incorporated in the metallic matrix. RTC analysis indicated that the preferred orientation of Ni-W/TiN was (111) texture. The crystallite size was of 10–16 nm, indicating the formation of nanocrystalline structure. TiN concentration, duty cycle and frequency could influence the amount of TiN particle and W element in the coating, then regulating hardness and anti-wear behaviors. The low duty cycle and long deposition time could diminish the roughness of the coating. The inclusion of TiN nanoparticles in the nickel matrix could promote the nucleation of fresh nickel crystals and restrict the growth of already formed nickel grains, favoring the homogeneous growth and grain refinement of Ni-W crystals. The doped TiN particles would favor the preferred orientation (111) plane, enhanced the hardness, wear and corrosion resistance of Ni-W alloy. Electrochemical results illustrated that the best corrosion-resistant properties of the nanocrystalline coating could be obtained at TiN 30 g L⁻¹, duty cycle of 20% and frequency of 60–200 Hz. The enhanced mechanical properties and corrosion resistance of Ni–W/TiN coating benefits its application in harsh corrosive environment.     

Effect of current density and deposition time on microstructure and corrosion resistance of Ni-W/TiN nanocomposite coating

Ni-W/TiN nanocomposite coatings were successfully prepared via pulse electroplating from an electrolyte containing suspended TiN nanoparticles. The effects of applied current density and deposition time on microstructure, morphology, composition, hardness and electrochemical behaviors of the obtained coatings were investigated. Results showed that the current density and deposition time affect remarkably the electrochemical co-deposition process and then the structure and characteristics of the composites. It illustrated that the nanocomposites are uniform, compact and crack-free. The nanocomposites prepared at I_a =?3?A?dm^?2 and t?=?20?min had the finest structure, showing a fine and smooth surface. EDS mapping and XPS spectra illustrated that the TiN nanoparticles had been homogeneously dispersed throughout the coating. 2.34?wt% TiN nanoparticles were embedded in Ni–W (68.56?wt% Ni and 29.1?wt%?W) alloy matrix at I_a=?3.0?A?dm^?2. The inclusion of TiN nanoparticles in Ni–W could promote the nucleation and cause a distinct microstructural change. The crystallite size was in the range of 11–15?nm. The average roughness value (R_a) is 65.7?nm and 73.8?nm for coating formed at 20?min and 40?min, respectively. The electrochemical measurements illustrated that I_a =?3–5?A?dm^?2 and t?=?40–60?min was the optimal operating parameters for the excellent anti-corrosion properties of Ni–W/TiN nanocomposites. The embedded TiN in Ni–W matrix could fill defects then improve its corrosion resistance. This electrodeposited Ni–W/TiN nanocomposites possess excellent hardness and superior corrosion resistance, and is expected to be applied in aggressive environment as a protective coating.     

Influence of the size of spraying powders on the microstructure and corrosion resistance of Fe-based amorphous coating

The Fe-based amorphous coatings with the composition of Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂ were successfully sprayed on mild steel substrate by the high velocity oxygen fuel (HVOF) spraying process with different feedstock powder sizes (i.e., powder A: −33 + 20 μm, powder B: −45 + 33 μm, powder C: −55 + 45 μm). The coatings were characterized for its morphology, microstructure and thermal stability by using X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The corrosion behavior of the coatings in 3.5 wt% NaCl solution was studied with potentiodynamic and potentiostatic polarization test. It was found that the particle size of the feedstock powders had a significant influence on microstructure and corrosion resistance of the resultant coatings. The coatings sprayed with the finest powders show the most compact structure; while the coating with the coarser powders exhibits a better corrosion resistance. It is found that the corrosion resistance of the coatings is closely related to the wetting behavior which is affected by the oxygen content and the roughness of coatings. The coatings with hydrophobicity exhibit a better corrosion. The present result demonstrates that the amorphous coatings with hydrophobicity and excellent corrosion resistant are promising for industrial application in marine environment.     

环氧／纳米ZnO复合涂层对镁锂合金耐腐蚀性的影响

以聚丙烯酰胺凝胶法制备了纳米ZnO,并对其进行改性,得到了环氧/纳米ZnO复合涂层.采用XRD和SEM对环氧/纳米ZnO复合涂层进行了表征.通过极化曲线和交流阻抗研究了裸基、复合涂层以及经锡酸盐转化处理后涂覆环氧/纳米ZnO的复合涂层的耐蚀性能.结果表明:复合涂层呈明显的两相结构,纳米ZnO分布均匀;复合涂层和锡酸盐转化协同,提高了镁锂合金的耐腐蚀性能.涂层中纳米ZnO质量分数不同,对镁锂合金耐蚀性能有不同的影响,纳米ZnO质量分数为2%时,复合涂层对镁锂合金的保护作用最强.     

Composite Ni/Al2O3 coatings and their corrosion resistance

Composite coatings Ni/Al₂O₃ were electrochemically deposited from a Watts bath. Al₂O₃ powder with particle diameter below 1 μm was codeposited with the metal. The obtained Ni/Al₂O₃ coatings contained 5-6% by weight of corundum. The structure of the coatings was examined by scanning electron microscopy (SEM). It has been found that the codeposition of Al₂O₃ particles with nickel disturbs the nickel coating's regular surface structure, increasing its microcrystallinity and surface roughness. DC and AC electrochemical tests were carried out on such coatings in a 0.5 M solution of Na₂SO₄ in order to evaluate their corrosion resistance. The potentiodynamic tests showed that the corrosion resistance of composite coating Ni/Al₂O₃ is better than that of the standard nickel coating. After 14 days of exposure the nickel coating corrodes three times faster than the Ni/Al₂O₃ coating. The electrochemical behaviour of the coatings in the corrosive solution was investigated by electrochemical impedance spectroscopy (EIS). An equivalent circuit diagram consisting of two RC electric circuits: one for electrode, nickel corrosion processes and the other for processes causing coating surface blockage, were adopted for the analysis of the impedance spectra. The changes in the charge transfer resistance determined from the impedance measurements are comparable with the changes in corrosion resistance determined from potentiodynamic measurements.     

Influence of UV weathering on corrosion resistance of prepainted steel

It has been observed that UV weathering and corrosion resistance tests are often performed separately, without taking into consideration their reciprocal influence. This is the case in the field of prepainted steel, where the European norm considers either UV durability or corrosion resistance. There is therefore no real evaluation of the global durability of the system. The aim of the present study is to show the influence of the photo-oxidation of painted layers on their barrier effect. This can lead to the formation of small blisters during field exposure. The blistering observed in natural exposure is never observed in individual accelerated corrosion tests. The depth of degradation from the surface of prepainted panels has been determined with infrared spectroscopy. Successive abrasions and FTIR analysis in ATR mode (attenuated total reflectance) allow us to determine oxidation profiles that can be well correlated with the decrease of barrier properties of painted systems measured with electrochemical impedance spectroscopy (EIS). The blistering has then been reproduced by exposing UV-weathered samples in a salt spray device.     

装饰用铜合金镧-铈复合化学转化工艺及膜层耐蚀性

对装饰用H62铜合金进行稀土镧-铈复合化学转化.对转化液组成和工艺条件进行正交优化,得到最优参数为:硝酸镧4 g/L,硝酸铈4 g/L,苯并三氮唑15 g/L,钼酸钠2 g/L,柠檬酸13 g/L,磺基水杨酸9 g/L,十二烷基苯磺酸钠0.4 g/L,温度53°C,时间4 min.该条件下所得La-Ce复合转化膜的厚度...     

Improved corrosion resistance of AZ91D magnesium alloy coated by novel cold-sprayed Zn-HA/Zn double-layer coatings

In order to improve the corrosion resistance and bioactivity of biodegradable Mg alloy substrate, novel Zn-HA/Zn double-layer coatings with different HA/Zn ratios in weight were deposited on AZ91D substrates by cold spraying. Phase compositions and microstructures of as-sprayed coatings and coatings after corrosion tests were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Electrochemical corrosion behaviors of both Zn-HA/Zn double-layer coatings were investigated in Hanks’ simulated body fluid using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Results showed that both the pure Zn coating and HA/Zn composite coatings presented the similar phase compositions with their primary powders in addition to Zn oxidizations. Zn powders were plastically deformed and partially oxidized due to its low melting point, while HA powders were mainly crashed into fragments and hill-like splats. Both Zn under layer and HA/Zn upper layer were well bonded and presented dense structures, differences in HA/Zn upper layers were related to the HA/Zn ratios. Potentiodynamic polarization and EIS measurements illustrated that the cold-sprayed Zn-HA/Zn double-layer coatings not only improve the corrosion resistance of Mg alloy substrates, but also enhance its bioactivity due to the HA existed in composite upper layer.     

Enhanced corrosion resistance of hydroxyapatite/magnesium-phosphate-composite-coated AZ31 alloy co-deposited by electrodeposition method

Magnesium-phosphate-doped hydroxyapatite (HAMP, Mg₃(PO₄)₂-Ca₁₀(PO₄)₆(OH)₂) and magnesium-hydrogen-phosphate-doped dicalcium-phosphate-dehydrate (DCPD-MHP, MgHPO₄-CaHPO₄) composite coatings were successfully electrodeposited onto an AZ31 alloy, and their corrosion behaviour was evaluated via electrochemical and in vitro degradation tests. In addition, the stability of the coatings was evaluated via these electrochemical tests. The results showed that the corrosion resistance and stability of the composite coatings were both significantly higher than those of single coatings; this greater resistance and stability resulted from the denser and more uniform structures of the composite coatings.     

High corrosion resistance of electroless composite plating coatings on AZ91D magnesium alloys

The process of electroless plating Ni-P on AZ91D magnesium alloys was improved. The Ni-P-ZrO₂ composite coatings and multilayer coatings were investigated based on the new electroless plating process. The coatings surface and cross-section morphologies were observed with scanning electron microscopy (SEM). The chemical compositions were analyzed by EDXS. The corrosion behaviors were evaluated by immersion, salt spray and electrochemical tests. The experimental results indicated that the Ni-P-ZrO₂ composite coatings suffered attack in NaCl solution but displayed passivation characteristics in NaOH and Na₂SO₄ solutions. The corrosion resistance of Ni-P-ZrO₂ coatings was superior to Ni-P coatings due to the effect of ZrO₂ nano-particle. The multilayer coatings consisting of Ni-P-ZrO₂/electroplating nickel/Ni-P (from substrate to surface) can protect magnesium alloys from corroding more than 1000 h for the salt spray test.