石墨烯对水性环氧富锌涂料中锌粉的取代能力研究

针对水性重防腐涂层体系中水性环氧富锌底漆高锌粉含量所带来的生产成本高、不易贮存、环境污染大等问题,采用在涂料中添加少量石墨烯以取代部分锌粉的改进方法。通过动电位极化曲线、电化学阻抗谱等方法研究了锌粉含量以及石墨烯添加量对环氧富锌涂料性能的影响,结果表明:涂层的耐腐蚀性随着锌粉含量增加而提高,锌粉占锌粉与硫酸钡总质量的80%时,腐蚀速率为0. 002 03毫米/年(mm/y),当涂层中锌粉占锌粉与硫酸钡的总质量的20%时,随着石墨烯添加量从占锌粉、硫酸钡与石墨烯总质量的0增加至0. 8%,腐蚀速率先上升后下降,当石墨烯含量达到0. 6%时,腐蚀速率为0. 0 038 mm/y,涂层的耐腐蚀性达到最大值。     

Corrosion protection with zinc-rich epoxy paint coatings embedded with various amounts of highly dispersed polypyrrole-deposited alumina monohydrate particles

Active anodic zinc content below 90 wt.% does not support sufficient electrical contacts but higher contents cause high porosity of traditional liquid zinc-rich paints (ZRPs). To resolve this problem, our proposal is the application of highly dispersed polypyrrole (PPy) coated alumina inhibitor particles (PCAIPs) in zinc-rich paint compositions. Using these nano-size inhibitor particles at concentrations from 4.55 to 0.85 wt.%, hybrid paints were formulated with zinc contents ranging from 60 to 85 wt.% at the same time. Submicron morphology and nano-scale structure, spectroscopy characteristics and electrochemical properties of the PCAIPs were studied by transmission electron microscopy (TEM) and rheology, Fourier-transform infrared spectroscopy (FT-IR) and cyclic voltammetry (CV) in first part of the work. In the second part, electrolytic corrosion resistivity of two sets of paint coatings were salt-spray chamber and immersion tested with 5 wt.% aqueous solution of sodium chloride. Active corrosion prevention ability of the salt-spray tested coatings was evaluated in compliance with ISO recommendations. Dielectric properties of the coatings during the immersion tests were monitored by electrochemical impedance spectroscopy (EIS). Corrosion tested area of the coatings was investigated by glow-discharge optical emission spectroscopy (GD-OES) to disclose infiltration of corrosive analytes and oxygen enrichment in the cross-section of the primers in comparison with their pristine states. Morphology of the zinc pigments was examined by scanning electron microscopy (SEM), and quality of steel specimens and the interfacial binder residues by X-ray photoelectron spectroscopy (XPS) as well as FT-Raman and Mössbauer spectroscopy. The results of both types of corrosion tests evidenced efficient utilisation of sacrificial anodic current for galvanic protection and improved barrier profile of the hybrid coatings, along with the PCAIP inhibited moderate self-corrosion of zinc. As a result of well balanced active/passive function, the hybrid coating containing zinc at 80 wt.% and PCAIPs at 1.75 wt.% embedding PPy at 0.056 wt.% indicated the most advanced corrosion prevention. Galvanic function of the hybrid paints is interpreted on the basis of size-range effect and spatial distribution of the alumina supported PPy inhibitor particles and basic electrical percolation model considerations.     

新型活化环氧富锌涂层的耐腐蚀性研究

富锌涂料在防腐蚀领域具有广泛应用,然而其长效防护性能却受到锌粉活性影响。本文以冷涂锌涂层、传统环氧富锌涂层作为对照,研究了新型具有电化学活性的环氧富锌涂层在盐雾加速腐蚀试验后的耐腐蚀性。宏观形貌分析表明:盐雾加速腐蚀1 800 h后,活化环氧富锌涂层表面并未出现锈点;采用扫描电子显微镜、维体式显微镜观察试验后涂层的表面形貌和涂层结构,发现活化环氧富锌涂层微观表面更加平滑,锌粉并未出现大面积的氧化,涂层内部大小锌粉颗粒均匀排列;通过电化学方法研究涂层的耐蚀机理与防护性,发现活化富锌涂层具有更持久的低防护电位。以上研究结果表明,较冷涂锌及传统环氧富锌涂层而言,新型活化环氧富锌涂层具有优异的长期防护性能,是值得关注和研究的一种新型技术。     

Electrochemical and anticorrosion performances of zinc-rich and polyaniline powder coatings

In this work, hydrochloride polyaniline (PANI-Cl) powder was incorporated as a conductive pigment into powder zinc-rich primer (ZRP) formulations in order to enhance the electronic conduction paths between zinc particles inside the coating and the steel substrate (i.e. percolation). Coatings were applied onto steel substrates and immersed in a 3% NaCl solution at ambient temperature.The protective properties and electrochemical behaviour of coatings were investigated by monitoring the free corrosion potential versus time and by using EIS. It was found that corrosion potential remains cathodic and constant for a long time up to 100 days of immersion. From EIS results, it was shown that the coatings exhibit larger impedance values than those observed with liquid or other zinc-rich powder formulations containing carbon black. From Raman spectroscopy results, it may be proposed that zinc particles in contact with PANI-Cl pigments were passivated. Other zinc particles remain still active which ensures the cathodic protection of the substrate. Moreover, coatings exhibit good barrier properties.     

A novel approach to heal the sol-gel coating system on magnesium alloy for corrosion protection

Sol-gel-based coatings exhibit high potentiality to be as an alternative to toxic chromate coatings for surface pre-treatment of metals and alloys. However, as soon as even small defects appear in the coating, the coating cannot stop the development of corrosion process. Present work demonstrates the possibility to use zinc nitrate as healing agent to repair the organic silane coatings in NaCl solution. The zinc nitrate was added to the 0.005 M NaCl solution where AZ91D magnesium alloy coated with organic silane coating was immersed. The healing process and the healing mechanism were investigated by electrochemical measurements and scanning electron microcopy coupled with energy dispersive spectroscopy. The results demonstrated the introduction of zinc nitrate to the electrolyte could stop the development of corrosion process of the coating system and a remarkable recovery on corrosion resistance could be obtained. This effect may be attributed to the formation of zinc oxide/hydroxide on the defective areas, hindering the corrosion activities.     

Studying the corrosion protection properties of an epoxy coating containing different mixtures of strontium aluminum polyphosphate (SAPP) and zinc aluminum phosphate (ZPA) pigments

Epoxy/polyamide coatings were loaded with different mixtures of strontium aluminum polyphosphate (SAPP) and zinc aluminum phosphate (ZPA) pigments. Moreover, a coating containing zinc phosphate (ZP) was prepared as a reference sample. The coatings were applied on St-37 steel substrates and then were exposed to 3.5 wt% NaCl solution up to 35 days. The corrosion inhibition properties of the pigments extracts were studied on bare steel samples by a potentiodynamic polarization technique after 24 h immersion. The morphological properties and corrosion resistance of the coatings were investigated by scanning electron microscope (SEM), optical microscope, electrochemical impedance spectroscopy (EIS) and salt spray tests.     

Application of EIS and salt spray tests for investigation of the anticorrosion properties of polyurethane-based nanocomposites containing Cr2O3 nanoparticles modified with 3-amino propyl trimethoxy silane

The Cr₂O₃ nanoparticles were modified with 3-amino propyl trimethoxy silane in order to obtain proper dispersion and increment compatibility with the polyurethane coating matrix. The nanocomposites prepared were applied on the St-37 steel substrates. The existence of 3-amino propyl trimethoxy silane on the surface of the nanoparticles was investigated by Fourier transform infrared (FTIR) spectroscopy and thermal gravimetric analysis (TGA). Dispersion of the surface modified particles in the polyurethane coating matrix was studied by a field emission-scanning electron microscope (FE-SEM). The electrochemical impedance spectroscopy (EIS) and salt spray tests were employed in order to evaluate the corrosion resistance of the polyurethane coatings. Polarization test was done in order to investigate the corrosion inhibition properties of the Cr₂O₃ nanoparticle on the steel surface in 3.5 wt.% NaCl solution. The adhesion strengths of the coatings were evaluated by pull-off adhesion tester before and after 120 days immersion in 3.5 wt.% NaCl solution. FT-IR and TGA analyses revealed that surface modification of the nanoparticles with 0.43 silane/5 g pigment resulted in the greatest amount of silane grafting on the surface of particles. Results obtained from FE-SEM analysis showed that the surface modified nanoparticles dispersed in the coating matrix properly. Results obtained from EIS and salt spray analyses revealed that the surface modified particles enhanced the corrosion protection performance of the polyurethane coating considerably. The improvement was more pronounced for the coating reinforced with 0.43 g silane/5 g pigment. Moreover, the adhesion loss decreased in the presence of surface modified nanoparticles with 0.43 silane/5 g pigment.     

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.     

Studies on plasma sprayed bi-layered ceramic coating on bio-medical Ti-13Nb-13Zr alloy

Biomedical Ti alloys are prone to undergo degradation due to the combined effect of wear and corrosion. To overcome these problems, surface modification techniques are being used. In this paper, the biomedical Ti alloy Ti-13Nb-13Zr was plasma sprayed with nanostructured Al₂O₃-13 wt%TiO₂, yttria stabilized zirconia powders and bilayer containing alternate layers of the two coatings to improve the corrosion resistance and microhardness of the substrate. The plasma sprayed coatings were characterized by X-ray diffraction, scanning electron microscopy and Raman spectroscopy. The microstructure, microhardness and surface roughness of the coatings were investigated. The corrosion resistance of the coatings was studied in simulated body conditions. The results show improved corrosion resistance for the bilayered coating compared to the individual plasma sprayed coatings on biomedical Ti-13Nb-13Zr alloy substrate.     

Preparation of PANI/epoxy/Zn nanocomposite using Zn nanoparticles and epoxy resin as additives and investigation of its corrosion protection behavior on iron

Conducting polyaniline, zinc and epoxy resin solely have anticorrosive properties by different mechanisms on metallic substrates. In this work the triple hybrid of PANI/epoxy/Zn nanocomposite was prepared as a thin layer coating (70 ± 5 μm) on iron coupons and its anticorrosion performance was investigated in HCl (0.1 M) as corrosive solution. Epoxy resin and zinc nanoparticles were applied as additives in the PANI matrix to improve the mechanical properties of PANI coating and investigate their synergetic effects on the anticorrosion performance of PANI coating. At first PANI/Zn nanocomposite coatings with different Zn contents were prepared and the zinc content optimized so that the coating achieve the best anticorrosion performance. Accordingly the iron coupons coated by PANI/Zn coating having 4 wt% Zn content showed more noble open circuit potential and lower corrosion current values. Then epoxy resin was applied as additive to the optimized formulation of PANI/Zn coating in different weight percents (0–20 wt%) and the anticorrosion performance of the related PANI/epoxy/Zn triple hybrid nanocomposite coatings was evaluated. Results showed that the addition of epoxy resin causes to the decreasing of corrosion current of iron samples coated by PANI/epoxy/Zn nanocomposite. An optimum range of 3–7 wt% was obtained for the epoxy content in the composition of PANI/epoxy/Zn nanocomposite in which the coating exhibits the best anticorrosion performance. Iron metal coupon was elementally analyzed and the PANI/Zn and PANI/epoxy/Zn nanocomposites were characterized using Fourier Transform Infrared spectroscopy, X-ray diffraction patterns and Scanning Electron Microscopy techniques.     

Effects of powder size and metallic bonding layer on corrosion behaviour of plasma-sprayed Al2O3-13% TiO2 coated mild steel in fresh tropical seawater

This study focuses on the effects of powder size and Ni–Al bonding layer on the electrochemical behaviour of plasma-sprayed Al₂O₃-13% TiO₂ coating in fresh tropical seawater. The presence of the metallic bonding layer reduces the coating porosity and increases the surface roughness for both microparticle and nanoparticle coatings. The nanoparticle exhibits better corrosion rate of 1.9×10⁻⁶ mmpy compared to the microparticle coating, with a corrosion rate of 3.05×10⁻⁶ mmpy. However, the presence of the metallic bonding layer increases the corrosion rate for both micro and nanoparticle coatings. The corrosion mechanism for the coating with and without the metallic bonding layer is discussed in detail.     

新型硅丙乳液在水性无机富锌涂料中的应用

利用乙烯基三乙氧基硅烷对电气石粉表面进行包覆改性,再以原位聚合的方式将其引入至硅丙乳液的聚合过程中,合成了一种新型硅丙乳液,并以此作为有机成膜物质,添加至无机硅酸钾溶液中,制得富锌涂料.通过扫描电镜(SEM)和能谱(EDS)对包覆改性后的电气石粉及其涂膜进行表征;使用电化学阻抗谱(EIS)测试了富锌涂层的耐蚀性.结果表...     

机械力表面改性对镁合金含铝涂层耐腐蚀性能影响的研究

在AZ91D镁合金表面涂覆含有铝粉的缩丁醛有机涂层，并对涂层表面进行机械力表面改性通过中性盐雾试验和W=5％的NaCl溶液浸泡试验研究了机械力表面改性和不同铝粉粒径对该涂层耐腐蚀性能的影响时涂层经机械力表面改性前后的微观形貌和NaCI溶液中的交流阻抗分踟进行了探讨结果表明，涂液中铝粉的粒径对涂层的耐蚀性有较大影响；该机械力表面改性处理可以增强有机涂层与基体的结合强度，提高涂层表面的致密程度．从而提高了涂层的耐腐蚀性能。     

Effect of nano-ZnO particles on the corrosion resistance of polyurethane-based waterborne coatings immersed in sodium chloride solution via EIS technique

Nano-composite coatings were formed by incorporating 3 wt% nano-ZnO in a polyurethane-based waterborne coating. The nano-ZnO based composite coatings were applied on standard phosphated steel panels by cathodic electrodeposition. The electrodeposited nano-composite coatings were then baked for 20 min at 165 °C. To investigate the corrosion resistance of the coatings, the coated panels were immersed in 3.5 wt% NaCl solutions for 2880 h (120 days). The improvement in corrosion performance of the composite coatings was evaluated using electrochemical impedance spectroscopy technique. It was found that the films containing nano-sized ZnO particles show a corrosion resistance of 2 orders of magnitude higher than that of the neat films.     

Effect of saccharin addition on the corrosion resistance of polypyrrole coatings

Electropolymerization baths for polypyrrole coating typically consist of two main constituents: monomer and counter-ion. By adding saccharin as the third constituent, a new branch emerges in electropolymerization that will yield coatings with modified properties. In the present study, polypyrrole is galvanostatically deposited onto carbon steel in an aqueous solution containing 0.2 M pyrrole and 0.1 M oxalic acid as the supporting electrolyte with (0.25, 0.5, 2.5 g/l) and without saccharin addition. Determination of the corrosion resistance of coatings in 0.1 M NaCl solution shows that in the presence of 0.5 g/l saccharin, a more noble corrosion potential and a greater corrosion resistance are obtained. Electrochemical impedance spectroscopy (EIS) revealed that the corrosion process was under infinite diffusion control of ions during prolonged immersion. The results indicate that the lower diffusion rate of ions in the coating produced in the presence of 0.5 g/l saccharin is responsible for its better corrosion resistance. Atomic force microscopy (AFM) shows that greater compaction of the coating produced in the presence of 0.5 g/l saccharin could be the reason for its higher corrosion resistance.     

改性环氧富锌底粉在高耐盐雾锈蚀方面的研究

防腐型熔结环氧粉末涂料与富锌环氧粉末涂料应用多年,但在很多高耐盐雾锈蚀环境仍无法完全替代溶剂型涂层.为提升粉末涂料耐盐雾性能,本研究通过对环氧富锌粉末涂料进行改性,在降低涂层体积电阻率的基础上提升牺牲阳极效率,使涂层达到液体涂料耐盐雾等级性能.结果 表明:添加0.2％导电材料单壁碳纳米管与30％片状锌粉以及其他功能助剂...     

Zinc deposited polymer coatings for copper protection

Polypyrrole (PPy) and polyaniline (PAni) coatings were electrosynthesized on copper, by using cyclic voltammetry technique. Then, these coatings were modified with the deposition of zinc particles from aqueous zinc sulphate solution. The electrodeposition of zinc was achieved at a constant potential value of −1.20 V, in the amount of ∼0.75 mg/cm². The corrosion performance of zinc modified polymer coatings were investigated in 3.5% NaCl solution; by using the electrochemical impedance spectroscopy (EIS), and anodic polarization curves. The zinc particles improved the barrier property of polymer films, thanks to formation of voluminous zinc corrosion products within the pores of polymer coating. Also, the zinc particles provided cathodic protection to the substrate, where the polymer film played the role of conductance between zinc particles and copper.     

Corrosion resistance and lifetime of polyimide-b-polyurea novel copolymer coatings

A novel class of polyurea-b-polyimide (PUI) block copolymer coating containing environmentally friendly aromatic polyurea has been successfully synthesized for corrosion protection of aluminum alloy 2024-T3 (Al 2024-T3). The PUI copolymer is able to self-assemble into a supramacromolecule by means of intra and inter-hydrogen bonds (H-bonds). The formation of H-bonds and effect of the later on the crystallinity of the copolymer was studied by using Fourier transform infrared spectroscopy (FTIR) and wide angle X-ray diffraction (WAXD). It was shown that increasing polyurea mole fraction up to 50 mol%, enhanced occurrence of H-bonding induced self-assembly, and resulted in remarkable enhancement in the degree of crystallinity, and corrosion resistance. Corrosion resistance and diffusivity of the copolymer coatings were investigated by electrochemical impedance spectroscopy (EIS), in a 3.5 wt% NaCl solution. The coating lifetime determined by using time-based corrosion resistance, was shown to be about 8 years for the optimized PUI copolymer coating. PUI coating synthesized by using 50 mol% of polyurea has a high contact angle (110°) and remarkably low surface energy of about 25.5 mJ/m².     

水性聚氨酯的蓖麻油和环氧改性及其富锌涂层耐蚀性能研究

以蓖麻油和环氧树脂为改性剂,对水性聚氨酯进行了改性,乳液红外分析证实了改性剂的有效接枝.改性后的聚氨酯其耐水性得到明显提高,吸水率降至3%以下.通过扫描电镜(SEM)、腐蚀电位和电化学阻抗谱(EIS)等方法对改性聚氨酯的富锌涂层进行了表征.结果表明,改性水性聚氨酯言锌涂料具有良好的耐蚀性;随着锌粉含量的增加,涂层耐蚀性提高.     

A study on the anticorrosion performance of the epoxy-polyamide nanocomposites containing ZnO nanoparticles

Epoxy nanocomposites were prepared using different loadings (2, 3.5, 5 and 6.5 wt%) of ZnO nanoparticles. Nanocomposites were applied on steel substrates. Samples were immersed in 3.5 wt% NaCl solution for 1344 h. Corrosion resistance of the coatings was studied by an electrochemical impedance spectroscopy (EIS). The effects of addition of nanoparticles on the mechanical properties of the epoxy coating were studied by a dynamic mechanical thermal analysis (DMTA). Curing behavior of the coatings containing nanoparticles was studied by a differential scanning calorimeter (DSC). Atomic force microscope (AFM) was utilized to investigate the surface topography and surface morphology of the coatings. Coating resistance against hydrolytic degradation was studied by FTIR (Fourier Transform Infrared).Results showed that addition of low loadings of nanoparticles can increase T_g of the composite. Decrease in T_g and cross-linking density of the coating were observed at high loadings of nanoparticles. It was found that nanoparticles can influence the curing behavior of the epoxy coating. Nanoparticles improved the corrosion resistance of the epoxy coating. Increase in coating resistance against hydrolytic degradation was obtained using nanoparticles.