镁合金表面Mg-MOF-74/硅烷复合涂层的制备及耐蚀性

通过水热合成法制备了微米级的金属有机骨架材料Mg-MOF-74粉体,采用浸渍提拉法在AZ31B镁合金表面制备了掺杂一定量Mg-MOF-74粉体的硅烷涂层。使用扫描电镜和红外光谱仪研究了Mg-MOF-74掺杂对硅烷涂层表面形貌和组织结构的影响。结果表明：相比于单纯的硅烷涂层,Mg-MOF-74/硅烷复合涂层更加平整致密;Mg-MOF-74中的羟基与水解后的硅烷脱水缩合生成了交联密度较高的网状结构,能够有效阻挡腐蚀介质向镁基底渗透。通过极化曲线测量、电化学阻抗谱测试、浸泡试验等方法研究了Mg-MOF-74/硅烷复合涂层的耐蚀性。与纯硅烷涂层相比,Mg-MOF-74/硅烷复合涂层的腐蚀电位正移了0.121 V,腐蚀电流密度下降了一个数量级,容抗弧半径明显增大,在模拟体液中浸泡13 d后的析氢量也下降了一半,表明Mg-MOF-74/硅烷复合涂层有效提高了镁合金基底的耐蚀性。     

Fault-tolerant hybrid epoxy-silane coating for corrosion protection of magnesium alloy AZ31

In this work, a hybrid epoxy-silane coating was developed for corrosion protection of magnesium alloy AZ31. The average thickness of the film produced by dip-coating procedure was 14 μm. The adhesion strength of the epoxy-silane coating to the Mg substrate was evaluated by pull-off tests and was found to be higher than 16 MPa both in dry and wet conditions. The hybrid epoxy-silane coating showed high corrosion resistance both when intact and when punched through by a needle. The low frequency impedance of intact coating was higher than 1 GΩ cm² after one month of immersion in 3.5% NaCl solution. Both, artificially induced defects and corrosion sites that appeared on the metal surface did not propagate. Their passivation behavior, that we call fault-tolerance, was observed by EIS, SVET-SIET and SEM-EDS. It was ascribed to the good adhesion, high coating integrity and corrosion inhibiting effect provided by diethylenetriamine used as epoxy hardener.     

氧化石墨烯/羟基磷灰石涂层对镁合金耐腐蚀性的影响

采用仿生法在改性模拟体液中于镁合金表面制备了羟基磷灰石(HA)涂层和氧化石墨烯/羟基磷灰石(GO/HA)复合涂层。利用扫描电子显微镜(SEM)和X射线衍射(XRD)对两种涂层进行了形貌和结构表征,通过析氢量测量、极化曲线和交流阻抗等方法分别研究了裸镁合金、含HA涂层及GO/HA涂层镁合金在pH为7.4的模拟体液(SBF)和3.5%NaCl溶液中的腐蚀行为。结果表明,氧化石墨烯增加了羟基磷灰石涂层的致密性,含GO/HA复合涂层的AZ91镁合金耐腐蚀性能最好,相对于裸镁合金,其腐蚀电流密度降低了一个数量级,析氢量降低了52%。     

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。     

A calcium phosphate coating improving corrosion resistance of the biodegradable magnesium alloy with graphene oxide modifying the deposition

Biodegradable magnesium alloy is an ideal material for medical implant applications, but its application is limited by its rapid degradation. Therefore, it becomes the main goal to improve corrosion resistance. In this study, a calcium phosphate dihydrate/graphene oxide composite coating was designed on the AZ60 alloy for medical applications. A calcium phosphate dihydrate coating was first prepared by biomimetic deposition on the alkali pretreated magnesium alloy, and graphene oxide was dispersed in the solution to modify the deposition. The results showed that graphene oxide could not only alter the loose striped calcium phosphate coating to the compact flaked composite coating, but also enhance the corrosion resistance with a reduced corrosion current density by 2 orders of magnitude, an increased impedance by 3 orders of magnitude and a corrosion rate down to 7/20. The in vitro biocompatibility of the composite coating was also demonstrated by a series cell experiments, with a cell viability of 120%. The composite coating provides a feasible method to enhance the corrosion resistance and biocompatibility of magnesium alloys.     

Effect of phytic acid on the microstructure and corrosion resistance of Ni coating

In this work, the pure Ni coatings were synthesized on Q235 steel by using reverse pulsed electrodeposition technique in sulphate-based baths with 0, 0.1, 0.2 and 0.3 g/L phytic acid additive. The effect of phytic acid on the microstructure and micro-morphology of the sample was observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. And the effect of phytic acid on the corrosion resistance of the sample was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results demonstrated that the addition of phytic acid was in favor of the growth of nano-scale twins (NT) in the interior of grains, which was due to the lowered stacking fault energies of Ni during the electrodeposition, and the typical morphology of pyramidal islands on the surface. The results also demonstrated that the effect of phytic acid was not monotonous with increasing concentration: the passive current density i_p was minimum and the charge transfer resistance R_t was maximum for the sample obtained from the bath with 0.2 g/L phytic acid, indicating that the sample obtained from the bath with 0.2 g/L phytic acid showed the best corrosion resistance.     

Electrochemical impedance spectroscopic investigation of the role of alkaline pre-treatment in corrosion resistance of a silane coating on magnesium alloy, ZE41

The protective performance of the coatings of bis-1,2-(triethoxysilyl) ethane (BTSE) on ZE41 magnesium alloy with different surface pre-treatments were evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 0.1 M sodium chloride solution. Electrical equivalent circuits were developed based upon hypothetical corrosion mechanisms and simulated to correspond to the experimental data. The morphology and cross section of the alloy subjected to different pre-treatments and coatings were characterized using scanning electron microscope. A specific alkaline pre-treatment of the substrate prior to the coating has been found to improve the corrosion resistance of the alloy.     

The corrosion resistance of 316L stainless steel coated with a silane hybrid nanocomposite coating

The present work aims at evaluating the corrosion resistance of 316L stainless steel pre-treated with an organic–inorganic silane hybrid coating. The latter was prepared via a sol–gel process using 3-glycidoxypropyl-trimethoxysilane as a precursor and bisphenol A as a cross-linking agent. The corrosion resistance of the pre-treated substrates was evaluated by neutral salt spray tests, linear sweep voltammetry and electrochemical impedance spectroscopy techniques during immersion in a 3.5% NaCl solution. In addition, the effect of the drying method as an effective parameter on the microscopic features of the hybrid coatings was studied using Fourier transform infrared spectroscopy and scanning electron microscopy. Results show that the silane hybrid coatings provide a good coverage and an additional corrosion protection of the 316L substrate.     

The corrosion resistance of 316L stainless steel coated with a silane hybrid nanocomposite coating

The present work aims at evaluating the corrosion resistance of 316L stainless steel pre-treated with an organic–inorganic silane hybrid coating. The latter was prepared via a sol–gel process using 3-glycidoxypropyl-trimethoxysilane as a precursor and bisphenol A as a cross-linking agent. The corrosion resistance of the pre-treated substrates was evaluated by neutral salt spray tests, linear sweep voltammetry and electrochemical impedance spectroscopy techniques during immersion in a 3.5% NaCl solution. In addition, the effect of the drying method as an effective parameter on the microscopic features of the hybrid coatings was studied using Fourier transform infrared spectroscopy and scanning electron microscopy. Results show that the silane hybrid coatings provide a good coverage and an additional corrosion protection of the 316L substrate.     

ZE10镁合金微弧氧化膜层的制备及耐蚀性研究

采用含硅酸钠14g/LK、氟化钠14g/L、氢氧化钠2g/L和甘油5 mL/L的电解液,以微弧氧化技术在ZE10镁合金的表面成功制备了微弧氧化膜.采用涡流测厚仪、扫描电镜、X射线衍射、电化学工作站等,研究了电压和时间对镁合金微弧氧化膜的厚度、表面形貌和耐蚀性的影响.结果表明,微弧氧化膜层主要由MgO、MgF2和Mg2S...     

Preparation and corrosion resistance studies of zirconia coating on fluorinated AZ91D magnesium alloy

Novel anti-corrosion zirconia coating was prepared via the sol–gel method for AZ91D magnesium alloy using zirconium nitrate hydrate as a precursor modified with acetylacetone (AcAc). Magnesium alloy substrates were first fluorinated in 20% HF aqueous solution at room temperature for 20 h, then, the zirconia coating was deposited on the fluorinated sample by dip coating. Basing on the sol–gel process, a chelate complex from the reaction of zirconium coordinating AcAc was formed which was supported by UV–vis spectrum analysis. The result showed that the absorption peak could be seen for the sol at 308 nm, which was red-shifted by 36 nm from that of methanol form of AcAc (272 nm). Moreover, Fourier transform infrared (FT-IR) spectrum analysis was performed to examine the structural differences between the gel and AcAc. The results indicated that the chelate complex with a bidentante structure was formed through the interaction chemically between zirconium nitrate and AcAc. The surface morphology of the zirconia coating was characterized by scanning electron microscope (SEM), an uniform coating can be obtained on the fluorinated sample. The corrosion resistance of the substrate, the fluorinated with and without the zirconia coating in the 3.5 wt.% NaCl solution was studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests, respectively. The results demonstrated that the zirconia coating could greatly improve the corrosion resistance of the AZ91D magnesium alloy. Furthermore, the effect of the different heat-treatment temperatures for the zirconia coating on corrosion resistance was also discussed.     

Conversion coating treatment for AZ31 magnesium alloys by a phytic acid bath

A phytic acid chemical conversion bath was applied to a sample of AZ31 magnesium alloy in this study; a transparent conversion coating formed subsequently on the sample surface. The test results of this coating with a scanning electron microscope (SEM) showed that there exist compact coatings on the surface of treated magnesium alloy. With the analyses of electronic probe microscopy (EPMA) and IR spectrum, a further study of this coating indicated that the coating was mainly composed of phytate and oxide or hydroxid. Furthermore, The electrochemical tests showed that the phytic acid bath conversion treatment enhanced the corrosion resistance of AZ31 magnesium alloys. The optimal pH of the phytic acid bath was 9.00–10.00.     

HMMM cured corrosion resistance waterborne ormosil coating for aluminum alloy

Due to the exceptional advantages of sol–gel process, organically modified silane (ormosil) coating has been applied to study the corrosion protection of aluminum alloy. In the present work, GPTMS/MTMS sol–gel solution was prepared by hydrolysis and condensation of 3-glycidoxypropyltrimetoxysilane (GPTMS) and methyltrimethoxysilane (MTMS) in aqueous solution of 0.05 M acetic acid in molar ratios 3:1. To prepare the ormosil coating solutions, a crosslinking agent hexamethoxymethylmelamine (HMMM) and a blocked acid catalyst p-toluenesulphonic (p-TSA) were combined with the sol–gel solution. Aluminum substrates were dip coated and cured at 130 °C for 45 min. Effectiveness of HMMM as a crosslinking agent was analyzed by evaluating corrosion resistance, chemical resistance and hydrophobicity of coating using potentiodynamic polarization method, immersion test and water contact angle, respectively. UV stability of sol–gel solution, ormosil coating formulation and coated substrate was also studied using UV–vis spectroscopy and UV-weatherometer to see performance of coating in outdoor application. Thermal behavior of ormosil was characterized using TGA and DSC. Surface morphology and structural characteristics were also characterized using SEM, AFM and FT-IR-RAS (reflection absorption spectroscopy). Pencil hardness, impact test and bend test were carried out to determine the adhesion, hardness and flexibility of coating.     

Effect of composite coating with poly-dopamine/PCL on the corrosion resistance of magnesium

We report the use of poly(ε-caprolactone) (PCL) and poly-dopamine (PD) as a protective coating that inhibits corrosion of the underlying magnesium metal. The PD coating layer also improved the adhesion of the PCL layer, which has been found to have a significant effect on corrosion behavior. In this study, electrochemical methods were employed to investigate the corrosion behavior of Mg after applying PCL composite coatings. Potentiodynamic polarization measurements determined that the PCL coating pretreated with PD effectively inhibited metal corrosion. In addition, the coating layer with improved adhesion has shown the possibility of inhibiting metal corrosion.     

Preparation and corrosion resistance of a self-sealing hydroxyapatite- MgO coating on magnesium alloy by microarc oxidation

An ideal self-sealing hydroxyapatite (HA)-MgO coating was designed on an AZ31 Mg alloy by one-step microarc oxidation (MAO) with the addition of HA nanoparticles into a base electrolyte. The formation mechanism of the self-sealing HA-MAO coating was discussed. The effect of the nano-HA addition on the corrosion resistance of the MAO coating was evaluated by corrosion tests in Hank's solution. The results show that HA nanoparticles inertly incorporated into the MAO coating during the process of coating growth. HA and MgO were the main constituents of the HA-MAO coating. The HA nanoparticles were absent in the inner barrier layer but concentrated in the outer porous layer. In addition, HA nanoparticles accumulated much more inside coating defects than in the other zones, which resulted in the nearly ideal sealing of micropores on the coating surface. By forming a denser and more stable outer layer, the incorporation of HA nanoparticles greatly enhanced the anti-corrosion properties of the MAO coating.     

有机添加剂对铝管表面硅烷涂层耐蚀性的影响

讨论了乌洛托品、植酸和吐温-80等3种有机添加剂在缓蚀液中对铝管表面硅烷涂层耐蚀性的影响.通过失重、析氢、盐雾试验和电化学阻抗(EIS)检测了铝管的耐蚀性.结果发现,有机添加剂的加入,使铝管的耐腐蚀性能大幅度提高,尤以乌洛托品为佳.在以乌洛托品为添加剂的缓蚀液里,铝管表面复合膜层均匀致密,中性盐雾试验达到420 h.初步探讨了缓蚀膜的成膜机理.     

铈对镁合金微弧氧化膜微观结构和耐蚀性的影响

利用扫描电镜、电化学工作站等,研究了不同铈盐添加方法对ZE10镁合金在由硅酸钠14 g/L、氟化钠14g/L、氢氧化钠2 g/L、甘油5mL/L组成的溶液中,于电压300 V、脉冲频率1 kHz、占空比15％的条件下微弧氧化20 min所得微弧氧化膜厚度、形貌和耐蚀性的影响.结果表明,先进行铈盐转化处理再微弧氧化和在电...     

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.     

Novel hybrid sol-gel coatings for corrosion protection of AZ31B magnesium alloy

This work aims to develop and study new anticorrosion films for AZ31B magnesium alloy based on the sol-gel coating approach.Hybrid organic-inorganic sols were synthesized by copolymerization of epoxy-siloxane and titanium or zirconium alkoxides. Tris(trimethylsilyl) phosphate was also used as additive to confer additional corrosion protection to magnesium-based alloy. A sol-gel coating, about 5-μm thick, shows good adhesion to the metal substrate and prevents corrosion attack in 0.005 M NaCl solution for 2 weeks. The sol-gel coating system doped with tris(trimethylsilyl)-phosphate revealed improved corrosion protection of the magnesium alloy due to formation of hydrolytically stable Mg-O-P chemical bonds.The structure and the thickness of the sol-gel film were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The corrosion behaviour of AZ31B substrates pre-treated with the sol-gel derived hybrid coatings was tested by electrochemical impedance spectroscopy (EIS). The chemical composition of the silylphosphate-containing sol-gel film at different depths was investigated by X-ray photoelectron spectroscopy (XPS) with depth profiling.