Interactions of BTESPT silane and maleic anhydride grafted polypropylene with epoxy and application to improve adhesive durability between epoxy and aluminium sheet

For improvement of adhesive strength and durability of adhesion between epoxy and aluminium sheet bis-(triethoxysilylpropyl)tetrasulfide (BTESPT) silane and maleic anhydride grafted polypropylene (PP-g-MAH) are chosen for surface pretreatment of the aluminium sheet respectively. Fourier transform infrared (FTIR) spectroscopy was used for characterization of the structure and the interactions in the systems. It is shown that BTESPT silane and the anhydride on PP-g-MAH take part in the curing reactions of the epoxy/polyamide system. The adhesive shear strength of the samples, prepared under different curing temperatures, and after immersion in boiling water and 3.5% NaCl water solution respectively, was tested. The features of the shear fractured surfaces were examined by scanning electron microscope (SEM). For the aluminium sheet pretreated by BTESPT silane, the maximum adhesive shear strength is 22.2 MPa, which is higher than that of 17.5 MPa for aluminium sheet without pretreatment by the silane. After immersion in boiling water for 80 h and in NaCl water solution at 50 °C for 180 h the adhesive shear strengths are 13.39 MPa and 18.4 MPa respectively, which are higher than these (below 6 MPa) for aluminium sheet without pretreatment by the silane. As for the aluminium sheet pretreated by PP-g-MAH, the maximum adhesive shear strength is 13.17 MPa. After immersion in boiling water for 80 h and in NaCl water solution at 50 °C for 180 h the adhesive shear strengths decline to 10.67 MPa and 8.1 MPa respectively.     

An elevated temperature infrared emissivity ceramic coating formed on 2024 aluminium alloy by microarc oxidation

An infrared emissivity coating material containing γ-Al₂O₃ was prepared on 2024 aluminium alloy surface by the microarc oxidation (MAO) method. The microstructure of the coatings was analysed by SEM, XRD and EDS techniques. The infrared emissivity properties tested at 500 °C were investigated by an infrared radiometer based on a Fourier transform infrared spectrometer. The results show that the infrared emissivity values of coated Al samples depend on the phase composition and surface roughness of the coatings. Corresponding to increasing coatings thickness, the gradually increasing γ-Al₂O₃ content and some oxide compounds containing Si and P contribute to the higher infrared emissivity value (about 0.85) in the wavelength range of 8–20 μm. The increasing surface roughness leads to an obvious increase in emissivity from 0.2 to 0.4 at wavelength 3–5 μm.     

Protective properties of cataphoretic epoxy coating on aluminium alloy AA6060 modified with electrodeposited Ce-based coatings: Effect of post-treatment

Ce-based conversion coatings (CeCCs) are a promising alternative to toxic chromate coatings on the metal substrates. In this work the CeCCs were electrodeposited on aluminium alloy AA6060 from aqueous solution of Ce(NO₃)₃ at different potentials (−0.95 V, −1.2 V and −1.4 V). Effect of deposition potential and post-treatment in the phosphate solution on morphology and protective properties of CeCCs with top cataphoretic epoxy coating was studied. To assess the differences between the protective systems, originating from the different CeCCs pre-treatments, electrochemical impedance spectroscopy (EIS), polarization measurements, AFM and SEM/EDS analysis were used. The EIS study was undertaken to follow the evolution of corrosion behaviour of epoxy coating/CeCCs protective systems over prolonged time of exposure to the chloride environment (3 wt.% NaCl). Results suggest significantly improved corrosion stability of epoxy coating on AA6060 with as-deposited CeCCs sub-layers with respect to the same epoxy coatings with phosphate post-treated CeCCs. The far best protective properties, i.e., the greatest value of pore resistance and the lowest value of corrosion current density were provided by the epoxy coating/CeCC protective system with CeCC deposited at −1.2 V and without post-treatment.     

AZ31镁合金表面防腐胶粘涂层的研制

胶粘涂层法是有效提高镁合金耐腐蚀性能的表面处理技术之一.以E-44环氧树脂、低分子量650#聚酰胺、云母氧化铁等为主要原料,制备了适用于AZ3l镁合金基体的防腐胶粘涂层.研究了填料含量对涂层外观、施工性和耐蚀性能的影响.结果发现,当填料质量分数为60%、涂层厚度为180～220μm时,防腐胶粘涂层具有良好的外观及施工性,附着力为1级,耐盐雾时间168 h.     

Electrochemical deposition and characterization of ZnCo alloys and corrosion protection by electrodeposited epoxy coating on ZnCo alloy

ZnCo alloys electrochemically deposited on steel under various deposition conditions were investigated. The influence of deposition current density, temperature and composition of deposition solution on the phase structure and corrosion properties of ZnCo alloys were studied. It was found that ZnCo alloy obtained from chloride solution at 5 A dm⁻² showed the best corrosion properties, so this alloy was chosen for further examination. Epoxy coating was electrodeposited on steel and steel modified by ZnCo alloy using constant voltage method. The effect of ZnCo alloy on the corrosion behavior of the protective system based on epoxy coating is interpreted in terms of electrochemical and transport properties, as well as of thermal stability.     

Investigation of corrosion protection properties of an epoxy nanocomposite loaded with polysiloxane surface modified nanosilica particles on the steel substrate

In this study, it has been aimed to investigate the corrosion protection properties of an epoxy/polyamide coating loaded with different concentrations (ranged from 3 to 6% (w/w)) of the polysiloxane surface modified silica nanoparticles (nano-SiO₂). The nanocomposites were applied on the steel substrates. Field emission scanning electron microscope (FE-SEM) and UV–vis techniques were utilized in order to investigate the nanoparticles dispersion in the coating matrix. The effects of addition of nanoparticles on the corrosion resistance of the coating were studied by an electrochemical impedance spectroscopy (EIS) and salt spray test. The coating surface degradation was studied by optical microscope and Fourier transform infrared radiation (FT-IR) spectroscopy. Results obtained from UV–vis and FE-SEM analyses revealed proper and uniform distribution of surface modified nanoparticles in the epoxy coating matrix. It was shown that the coating corrosion protection properties were significantly enhanced in the presence of 5 wt% silica nanoparticles. Less degradation occurred on the surface of the coatings loaded with 5 wt% nanoparticles.     

Effect of surface pre-treatment on surface characteristics and adhesive bond strength of aluminium alloy

In this work aluminium alloy surfaces have been subjected to three different methods of surface pre-treatments such as solvent degreasing, FPL (Forest Products Laboratory) etching and priming using an epoxy based primer. The treated surfaces were evaluated for surface energy, contact angle, surface topography, surface roughness and adhesive strength characteristics. The influence of surface pre-treatments on the variation of polar, dispersive and total surface energy of the surfaces is addressed. A wettability test was performed on the surfaces using an epoxy adhesive in order to assess the influence of the pre-treatment techniques on substrate/adhesive interaction. Theoretical work of adhesion values for the various pre-treated surfaces were calculated using the contact angle data and further tested experimentally by adhesive bond strength evaluation by tensile testing of a single lap aluminium-epoxy-aluminium assembly. The method of surface pre-treatment showed a profound effect on the surface topography and roughness by AFM. This study reveals that a combination of high surface energy and high surface roughness of the substrate along with good wettability of the adhesive contributed to the highest joint strength for the aluminium alloy through the FPL etching pre-treatment.     

铝合金稀土转化膜成膜因素对膜层性能的影响

通过正交实验研究了铝合金稀土化学转化膜成膜因素对转化膜性能的影响,获得了以下最佳配方:ρ(CeCl3)= 15 g／L,H2O2的体积分数为50 mL／L,ρ(柠檬酸)=2 g／L,θ=50℃。实验结果表明,H2O2的含量对转化膜厚度和硬度的影响最为显著,在体积分数为50 mL／L时膜厚和硬度的值最大;CeCl3的质量浓度对膜层厚度和膜层Rp值影响较大,随CeCl3浓度的升高膜厚和邱值增加;温度对膜层阻抗谱影响较为明显,随温度升高Rp值下降;柠檬酸的含量对膜层硬度和Rp值都有较大的影响,当其质量浓度为2 g／L时,所得膜层硬度最大、Rp值最高。     

Influence of the curing temperature of a cataphoretic coating on the development of filiform corrosion of aluminium

Aluminium alloys are known to be particularly sensitive to filiform corrosion. The initiation of this particular type of corrosion is related to different parameters such as the presence of defects, the permeability of the coating to water and oxygen, the adherence of the paint system and the presence of salts.

In this work, the filiform corrosion resistance of Al 6016 substrates coated with a cataphoretic paint was studied. The curing of the coating was performed at different temperatures (185, 175, 165, 155 and 135 °C) in order to modify its mechanical properties and its permeability to oxygen.

The paint properties were studied by different techniques allowing the estimation of the degradation of the metal–primer system and giving some information about intrinsic paint properties.

The corrosion protection of the coating was evaluated by a normalized filiform corrosion test and by electrochemical impedance spectroscopy on scratched samples. The glass transition value and the internal stresses of the cataphoretic coatings obtained for different curing temperatures were determined by a stressmeter equipment.

This study enabled us to underline the influence of the curing temperature on the intrinsic properties of the coatings such as the glass transition temperature, the internal stresses, the adherence, the permeability and the corrosion protection properties.     

环氧有机涂层对锌铁合金镀层耐蚀性的影响

利用腐蚀浸泡实验、失重法和交流阻抗谱分析等方法研究了环氧有机涂层对Q235钢电镀锌铁合金镀层耐蚀性的影响。结果表明,Q235钢基体、Q235+Zn–Fe合金镀层试样和Q235+Zn–Fe合金镀层+环氧有机涂层试样在5%NaCl溶液中浸泡504 h后,腐蚀速率分别为0.068 0、0.040 0和0.018 0 mm/a。涂覆环氧有机涂层至少能使锌铁合金镀层的防腐性能提高2倍,从而延长基体材料的使用寿命。     

镁合金表面合金化及电泳涂装工艺

介绍了镁合金表面合金化及电泳涂装工艺流程。讨论了镁合金表面合金化的工艺配方及其操作步骤。研究了镁合金的前处理、防腐涂装以及装饰性涂装工艺条件及其涂膜性能。为镁合金产品的防腐装饰提供了新的途径。     

镁合金表面草酸盐化学转化膜的性能研究

给出了镁合金表面处理的工艺配方,研究了草酸盐化学转化膜的微观形貌、结合力、导电性及抗蚀性.结果表明,转化膜由均匀细小、比较致密的颗粒构成,擦拭试验超过50次无颜色变化,试样表面的电阻率小于0.1 Ω·cm,盐雾试验超24h,性能达到使用标准.     

The effect of cataphoretic and powder coatings on the strength and failure modes of EN AW-5754 aluminium alloy adhesive joints

The aim of this study is to determine the effect of cataphoretic and powder coatings and also the method of application the primer on the adherends surface on the strength and failure modes of EN AW-5754 aluminium alloy adhesive joints. The study is performed on lap joints made of EN AW-5754 aluminium alloy, subjected to three different types of surface treatment; namely a) polyurethane cataphoretic coating, b) powder coating based on black mat RAL 9005 UL polyester resin and c) no coating. The tested adhesive joints were made using a one-component polyurethane adhesive Terostat 8596, which was dedicated for automotive and cured under a constant load of 0.018 MPa at 20 ± 2 °C. In addition, this study investigates the effect of the application of Terostat 8519P adhesion promoter which is a liquid polyurethane-based primer containing solvents and which is corresponding to Terostat 8596 polyurethane adhesive. Terostat 8519P adhesion promoter was applied in two different ways: a) to one substrate and b) to both substrates. The produced adhesive joints were subjected to strength tests using the Zwick/Roell Z150 testing machine. The examination of fracture in the tested adhesive joints was performed in accordance with the EN ISO 10365 standard. The shear strength results have demonstrated that both the method of application of the adhesion promoter (Terostat 8519 P) and the presence of cataphoretic coating had an influence on adhesive joints strength. The use of the adhesion promoter significantly affects the strength of both uncoated EN AW-5754 aluminium alloy adhesive joints and the adhesive joints subjected to powder coating. The use of the adhesion promoter has a less significant effect on the cataphoretic-coated samples.     

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.     

Effect of adhesive thickness and surface roughness on the shear strength of aluminium one-component polyurethane adhesive single-lap joints for automotive applications

Adhesively bonded technology is now widely accepted as a valuable tool in mechanical design, allowing the production of connections with a very good strength‐to‐weight ratio. The bonding may be made between metal–metal, metal–composite or composite–composite. In the automotive industry, elastomeric adhesives such as polyurethanes are used in structural applications such as windshield bonding because they present important advantages in terms of damping, impact, fatigue and safety, which are critical factors. For efficient designs of adhesively bonded structures, the knowledge of the relationship between substrates and the adhesive layer is essential. The aim of this work, via an experimental study, is to carry out and quantify the various variables affecting the strength of single-lap joints (SLJs), especially the effect of the surface preparation and adhesive thickness. Aluminium SLJs were fabricated and tested to assess the adhesive performance in a joint. The effect of the bondline thickness on the lap-shear strength of the adhesives was studied. A decrease in surface roughness was found to increase the shear strength of the SLJs. Experimental results showed that rougher surfaces have less wettability which is coherent with shear strength tests. However, increasing the adhesive thickness decreased the shear strength of SLJs. Indeed, a numerical model was developed to search the impact of increasing adhesive thickness on the interface of the adherend.     

钛植入合金表面电化学沉积掺镁羟基磷灰石涂层

以Ca(NO3)2、(NH4)2HPO4和Mg(NO3)2为原料,采用电化学沉积法在医用钛合金表面制备了掺镁羟基磷灰石涂层,研究了电沉积工艺条件对掺镁羟基磷灰石涂层表面形貌的影响。结果表明,当电流密度为1.0mA/cm2,温度为65°C,pH为4.5,n(Mg):n(Ca)=1:3,电沉积时间为1300s时,得到了均匀致密的晶须状涂层。X射线衍射分析表明,烧结后的掺镁羟基磷灰石涂层中Mg2+取代了Ca2+,使HA涂层的晶格发生了变化。     

Preparation of epoxy–clay nanocomposite and investigation on its anti-corrosive behavior in epoxy coating

An epoxy–clay nanocomposite was synthesized using a quaternary ammonium-modified montmorillonite clay and diglycidyl ether of bisphenol A (DGEBA) type epoxy resin, in order to produce anti-corrosive epoxy coating. Anti-corrosive properties of the nanocomposite were investigated using salt spray and electrochemical impedance spectroscopy (EIS) methods. The results showed an improvement in the barrier and anti-corrosive characteristics of epoxy-based nanocomposite coating and a decrease in water uptake in comparison with pure epoxy coating. Wide-angle X-ray diffraction (WAXD) patterns and transmission electron microscopy (TEM) analysis showed that the interlayer spacing of clays increased after addition of epoxy resin along with applying shear force and ultrasound sonicator. The best performance of this coating was achieved at 3 and 5 wt.% clay concentration.     

Polyurethane paint adhesion improvement on aluminium alloy treated by plasma jet and dielectric barrier discharge

The effect of atmospheric pressure plasma treatment on the adhesion between a protective coating and AA1100 alloy was investigated. Two plasma sources were used for surface modifications: atmospheric pressure plasma jet and dielectric barrier discharge. The surface roughness and water contact angle measurements were conducted in order to evaluate the changes on the aluminium surface after plasma processing. The paint coating was tested using the adhesion tape test (ASTM D3359). A significant improvement of surface wettability and adhesion was obtained after plasma treatments.     

钛合金搪瓷涂层的制备与性能研究

在钛合金表面制备搪瓷涂层,并对其性能进行了研究。结果表明,搪瓷涂层具有较好的抗高温氧化性及抗热震性,能有效提高钛合金的抗腐蚀能力,使其在700°C熔融盐(Na2SO4+NaCl)浸没100h而免遭腐蚀。     

Studying the influence of nano-Al2O3 particles on the corrosion performance and hydrolytic degradation resistance of an epoxy/polyamide coating on AA-1050

The aim of this work was studying the effects of addition of Al₂O₃ nanoparticles on the anticorrosion performance of an epoxy/polyamide coating applied on the AA-1050 metal substrate. For this purpose, the epoxy nanocomposites were prepared using 1, 2.5 and 3.5 (w/w) pre-dispersed surface modified Al₂O₃ nanoparticles. Field-emission electron microscope (FE-SEM) and ultraviolet–visible (UV–Vis) techniques were utilized in order to evaluate the nanoparticles dispersion in the epoxy coating matrix. The anticorrosion performance of the nanocomposites was studied by electrochemical impedance spectroscopy (EIS) (in 3.5 wt% NaCl solution for 135 days immersion) and salt spray test for 1000 h. The coating resistance against hydrolytic degradation was also studied by optical microscope and Fourier-transform infrared spectroscopy (FTIR). Results obtained from FE-SEM micrographs and UV–visible spectra showed that the nanoparticles dispersed in the coating matrix uniformly with particle size less than 100 nm even at high loadings. Results revealed that nano-Al₂O₃ particles could significantly improve the corrosion resistance of the epoxy coating. Nanoparticles reduced water permeability of the coating and improved its resistance against hydrolytic degradation.