Characterization and corrosion resistance of organically modified silicate/MO2 (M = Zr,Ti, or Ce) hybrid coatings on a 6061‐T6 aluminum alloy

Hybrid coatings based on organically modified silicate (Ormosil)/ZrO₂ (0–1.0 wt %) and Ormosil/MO₂ (M = Ti or Ce) were synthesized through a sol–gel technique. Tetraethylenepentamine, 3‐glycidoxypropyltrimethoxysilane, tetraethoxysilane, and MO₂ (M = Zr, Ti, or Ce) metallic particle were used as precursors for the hybrid coatings. These hybrid films were deposited via spin coating onto an aluminum alloy to improve the corrosion protection. The effects induced by the ZrO₂ content and the metallic particle type on the chain dynamics, thermal stability, and corrosion performance of the coated samples were investigated. The rotating‐frame spin–lattice relaxation times and scale of the spin–diffusion path length indicated that the configuration of the hybrid films was highly crosslinked and dense and adhered to the aluminum alloy substrates. The thermal stability and the apparent activation energy, evaluated by van Krevelen's method, of the hybrid coatings depended on the ZrO₂ content and on the metallic particle type. Potentiodynamic and salt‐spray analysis revealed that the hybrid films provided exceptional barrier and corrosion protection in comparison with untreated aluminum alloy substrates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 335–342, 2006     

Synthesis, infrared stealth and corrosion resistance of organically modified silicate-polyaniline/carbon black hybrid coatings

Hybrid coatings based on organically modified silicate-polyaniline/carbon black (Ormosil-PANI/CB) were synthesized through a sol-gel technique with different carbon black (10-30 wt%) and PANI/CB (10-30 wt%) contents. These hybrid films were deposited via spin coating onto an aluminum alloy in order to improve the corrosion protection and to act as infrared stealth coatings. The effects induced by the PANI/CB composites on the chain dynamic, thermal properties, infrared stealth, and anticorrosion performances of the coated samples were investigated. The rotating-frame spin-lattice relaxation times and scale of the spin-diffusion path length indicated that the configuration of the hybrid films was highly cross-linked and dense. Thermal properties of these Ormosil-PANI/CB hybrids have been improved over the pure Ormosil analyzed by thermal gravimetric analysis (TGA). The thermal extinction of the hybrid coatings increased with the increase in the carbon black and PANI/CB content. Potentio-dynamic and salt-spray analysis revealed that the hybrid films provided an exceptional barrier and corrosion protection in comparison with untreated aluminum alloy substrates.     

Infrared stealth and anticorrosion performances of organically modified silicate‐NiZn ferrite/polyaniline hybrid coatings

Hybrid coatings based on organically modified silicate‐Ni_0.5Zn_0.5Fe₂O₄/polyaniline were synthesized through a sol–gel technique with different NiZn ferrite/polyaniline weight ratio (1/1, 1/2, 1/5). These hybrid films were deposited via spin coating onto an aluminum alloy to improve the corrosion protection and to act as infrared stealth coatings. The effects induced by the NiZn ferrite/polyaniline hybrids on the chain dynamic, ferromagnetic behavior, infrared stealth, and anticorrosion performances of the coated samples were investigated. The rotating‐frame spin‐lattice relaxation times and scale of the spin‐diffusion path length indicated that the configuration of the hybrid films was highly cross‐linked and dense. The thermal extinction of the hybrid coatings increased with the increase in the polyaniline content. Potentio‐dynamic and salt‐spray analysis revealed that the hybrid films provided an exceptional barrier and corrosion protection in comparison with untreated aluminum alloy substrates. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 926–935, 2008     

Effect of ceria and zirconia nanoparticles on mechanical behavior of nanocomposite hybrid coatings

Epoxy-silica based hybrid nanocomposite coatings have been developed with different organicinorganic contents by sol–gel process. Various ratios of ceria and zirconia colloidal dispersions as inorganic nanoparticles are uniformly distributed in the hybrid sol. The hybrid sols are prepared by hydrolysis and condensation of 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetraethylorthosilicate (TEOS) in acidic solution using bisphenol A (BPA) and 1-methyl-imidazol (MI). A thin layer of each sol is coated on a micro-glass slide and 1050 aluminum alloy as substrates. The effect of alkoxysilane precursors (i.e. TEOS and GPTMS) and inorganic to organic molar ratio are investigated. Nanoindentation and dynamic mechanical analysis (DMA) performed to characterize the mechanical properties of the coatings in nanorange scale. It is revealed that all hybrid nanocomposite coatings had appropriate flexibility and strong interfacial interaction with the aluminum alloy substrate. It is proposed that the ceria and zirconia nanoparticles can be bonded to the surrounding of siloxane ring which can be induced high restriction in polymeric chain mobility in dynamic mechanical analysis. Nanoindentation tests showed that by increasing the inorganic phase in the nanocomposite, both elastic modulus and hardness increase, especially they are very intense in the higher levels of inorganic content.     

含氟高分子/SiO_2杂化疏水材料的制备及涂层表面性质

采用自由基溶液聚合与溶胶-凝胶法相结合的方法制备了含氟高分子/SiO2杂化疏水材料.通过甲基丙烯酸十二氟庚酯(FA)与乙烯基三乙氧基硅烷(VTES)共聚合成了含氟硅共聚物(PFAS),进一步通过原硅酸乙酯(TEOS)与PFAS共聚物溶液共水解缩聚制备了具有含氟侧基的碳碳主链高分子和硅氧网络的含氟高分子/SiO2杂化疏水材料.研究结果表明,SiO2组分含量提高可以显著增加杂化材料薄膜的涂敷厚度,改善其耐久性能,而对杂化材料疏水性能的影响不大.     

Improvement of Corrosion Resistance of Metals by an Environmentally Friendly Silica Coating Method

Corrosion resistance of stainless steel and Zn plated steel can be improved by a chromium-free environmentally friendly chemical solution deposition method. Precursor solutions were prepared from tetraethoxysilane with polymer, and were deposited on stainless steel, Zn plated steel and aluminum alloy by dip coating, followed by heat treatment. Addition of polymer to the precursor solution proved very effective in preparing films free from cracks on stainless steel and aluminum alloy substrates. The corrosion resistance was greatly improved by the resulting sub-micron thick silica-polymer hybrid film coatings on stainless steel and on Zn plated steel prepared at 200°C. The hardness of aluminum alloy coated with silica-PMMA hybrid film was improved by 7% over uncoated alloy.     

Inorganic–organic sol gel hybrid coatings for corrosion protection of metals

Inorganic–organic hybrid coatings by sol–gel process are very suitable for fighting corrosion. Inorganic sols in hybrid coatings not only increase adhesion by forming chemical bonds between metals and hybrid coatings, but also improve comprehensive performances of polymer in the coatings. Different organic polymers or organic functionalities are introduced into gel network to achieve tailored properties, such as hydrophobic properties, increasing cross-linking density, etc. As for corrosion protection of metals organic components of hybrid coatings are selected to repel water and form dense thick films and reduce coating porosity. The factors, such as the ratio of inorganic and organic components, cure temperature, pigments in hybrid coatings, need to be optimized for attaining hybrid films with the maximum corrosion resistance. Electro-deposition technique offers relatively thick homogeneous defect-free hybrid coatings in comparison to dip or spin coating techniques. Green cerium ions and non-ionizable organic inhibitors are more developed in hybrid coatings nowadays than other corrosion inhibitors. Long-term corrosion resistance techniques of inhibitors are discussed. The inhibitors entrapped in the nanocontainers are doped in hybrid films to prolong release of the inhibitors to damaged zones, which is discussed in detail. Among all the nanocontainers of corrosion inhibitors the prospective techniques which show superior corrosion protection are cyclodextrin/organic inhibitor inclusion complexes and layer by layer assembly of organic corrosion inhibitors in nanocontainers. Super-hydrophobic property of hybrid coatings derives from low surface tension and surface roughness of hybrid coatings, which endues the films with excellent corrosion protection for metals, but the durable property of super-hydrophobic coatings needs to be improved for industrial application. An ideal multiple model of hybrid coatings for superior anti-corrosion of metals proposed is a combination of super-hydrophobic hybrid coatings and underlying hybrid coatings doped with sustained release of corrosion inhibitors on metal substrates.     

Sol-Gel Coatings for the Protection of Brass and Bronze

The effectiveness of sol-gel Ormosil coatings as barriers coatings has already been demonstrated, and it is natural to assume that such coatings can play a unique role in art conservation, where object corrosion and decay are often a major issue. The main feature of ormosil coatings that would make them preferable to polymers is their potentially higher stability to ultra-violet radiation, controlled porosity and good adhesion to many different substrates. The permeability to various gases can also be tailored with changes in the chemical structure. In previous work, we have applied the sol-gel process as part of a multiplayer coating in the conservation of the Last Judgment mosaic in Prague. In the present work, we explore the use of sol-gel organic-inorganic hybrid coatings on various copper alloy substrates frequently encountered in art conservation.     

Thermal and neutron shielding properties of 10B containing UV cured hybrid coatings

¹⁰B containing organic–inorganic hybrid coating material based on a UV-curable formulation was prepared via anhydrous sol–gel technique. UV curable coatings were applied on Plexiglas (PMMA) substrates. The molecular structure of the coating material was analyzed by ATR-FTIR spectroscopy technique. The characterization of the UV-curable coating was evaluated by various techniques such as gel content, abrasion resistance, chemical resistance, pencil hardness, pendulum hardness, MEK rubbing test, contact angle, cross-cut test, gloss, transmittance test, neutron absorption, Limiting Oxygen Index and stress–strain tests. Hybrid coatings showed a significant enhancement in radiation shielding properties. The thermal behavior of coatings was also evaluated. It is observed that the thermal stability of coatings mainly depends on their boron and silicate contents. Results of all analysis conducted on hybrid films, and coatings were discussed.     

Sol-Gel Processing of Organic-Inorganic Nanocomposite Protective Coatings

Organic-inorganic nanocomposite protective coatings are prepared on aluminum substrates by the spinning technique with the concept of incorporating homogeneously nanosized particles (of AlOOH, Al2O3, ZrO2, SiC) into molecular organic-inorganic hybrid matrices. The hybrid matrices are prepared from epoxysilane and bisphenol A with imidazol as catalyst. The AlOOH particles are derived from aluminum isoprooxide and introduced into the hybrid sols directly, and Al2O3, ZrO2, SiC particles are first surface-modified with Si–OH from hydrolyzed TEOS. The coatings are dense, smooth and flexible and inhibit corrosion.     

Composite film coatings based on epoxy-polysiloxane systems of cationic polymerization and their anticorrosion properties

The anticorrosion properties of epoxy-polysiloxane coatings on the surface of the aluminum alloy D-16 were studied by a potentiodynamic method. It was established that the use of the hybrid coating led to an increased corrosion resistance from 0.250 kΩm·cm² for uncoated alloy to 0.396-0.996 kΩm·cm² for the coated aluminum support. The yield of the sol fraction, the micro hardness, and the glass transition temperature of the polymers were determined.     

Cross‐linked waterborne alkyd hybrid resin coatings modified by fluorinated acrylate‐siloxane with high waterproof and anticorrosive performance

Waterborne alkyd resin coatings are ideal for use as corrosion protection coatings because of its high cost‐effective and environmental advantages. However, their uses are restricted to general applications due to their poor acid, water, and alkali resistance. In this work, waterborne alkyd hybrid resins modified with fluorinated acrylate‐siloxane were synthesized via a surfactant‐free miniemulsion polymerization process using maleic anhydride and silicon modified alkyd resin, dodecafluoroheptyl methacrylate, methyl methacrylate, and butyl acrylate as monomers. And then, crosslinking alkyd resin films were prepared at room temperature using trimethylolpropane‐tris‐(β‐N‐azir‐idinyl) propionate (XR‐100) as the crosslinking agent. The acquired films had lower water absorption and higher water contact angles and had better mechanical/thermal properties, as well as good waterproof property. Most importantly, the electrochemical corrosion studies revealed that the cross‐linked coating exhibited superior corrosion resistance performance with an inhibition efficiency of 99.95% and a corrosion rate of 6.95 × 10^?3 mm per year.     

Synthesis and characterization of UV‐curable phosphorus containing hybrid materials prepared by sol–gel technique

In this study, a series of ultraviolet (UV)‐curable organic–inorganic hybrid coating materials containing phosphorus were prepared by sol–gel approach from acrylate end‐capped urethane resin, acrylated phenyl phosphine oxide oligomer (APPO), and inorganic precursors. TEOS and MAPTMS were used to obtain the silica network and Ti:acac complex was employed for the formation of the titania network in the hybrid coating systems. Coating performance of the hybrid coating materials applied on aluminum substrates was determined by the analysis techniques, such as hardness, gloss, impact strength, cross‐cut adhesion, taber abrasion resistance, which were accepted by international organization. Also, stress–strain test of the hybrids was carried out on the free films. These measurements showed that all the properties of the hybrids were enhanced effectively by gradual increase in sol–gel precursors and APPO oligomer content. The thermal behavior of the hybrid coatings was investigated by thermogravimetric analysis (TGA) analysis. The flame retardancy of the hybrid materials was examined by the limiting oxygen index (LOI); the LOI values of pure organic coating (BF) increased from 31 to 44 for the hybrid materials containing phosphorus (BF‐P:40/Si:10). The data from thermal analysis and LOI showed that the hybrid coating materials containing phosphorus have higher thermal stability and flame resistance properties than the organic polymer. Besides that, it was found that the double bond conversion values for the hybrid mixtures were adequate in order to form an organic matrix. The polycondensation reactions of TEOS and MAPTMS compounds were also investigated by ²⁹Si‐NMR spectroscopy. SEM studies of the hybrid coatings showed that silica/titania particles were homogenously dispersed through the organic matrix. In addition, it was determined that the hybrid material containing phosphorus and silica showed fibrillar structure. Copyright © 2009 John Wiley & Sons, Ltd.     

Anticorrosive cerium-based coatings prepared by the sol–gel method

The development of efficient anti-corrosion and environmentally friendly coating systems are needed for the replacement of the highly toxic Cr-based conversion coatings for corrosion protection of aluminum alloys. In this study, we demonstrate that the direct application of ceramic cerium-based sol–gel coatings to AA7075-T6 substrates produces high-performance anti-corrosion layers. Electrochemical experiments and analyses of the microstructure demonstrate that the protective layers are very efficient for the passivation of the alloy surfaces operating as both passive and active barrier for corrosion protection.     

铝合金表面原位自组装超疏水膜层的制备及耐蚀性能

采用阳极氧化法在铝合金表面原位构造粗糙结构, 经表面自组装硅氧烷后得到超疏水自清洁表面, 与水滴的接触角最大可达157.5°±2.0°, 接触角滞后小于3°. 通过傅立叶变换红外(FT-IR)光谱分析仪、场发射扫描电子显微镜(FE-SEM)、能谱仪(EDS)、原子力显微镜(AFM)和接触角测试对阳极氧化电流密度、硅氧烷溶液中水的含量和自组装时间等参数进行了分析, 并得到制备超疏水自清洁表面的最优工艺参数. FE-SEM及AFM的测试结果表明, 由自组装硅氧烷膜层的无序性形成的纳米结构和阳极氧化构造的微米级粗糙结构与硅氧烷膜层的低表面能的协同作用构成了稳定的超疏水表面. 电化学测试(动电位极化)的结果表明, 原位自组装超疏水膜层极大地提高了铝合金的耐蚀性.     

Inhibition effect of cerium in hybrid sol–gel films on aluminium alloy AA2024

Aluminium alloys such as AA2024 are susceptible to severe corrosion attack in aggressive solutions (e.g. chlorides). Conversion coatings, like chromate, or rare earth conversion coatings are usually applied in order to improve corrosion behaviour of aluminium alloys. Methacrylate‐based hybrid films deposited with sol–gel technique might be an alternative to conversion coatings. Barrier properties, paint adhesion and possibly self‐healing ability are important aspects for replacement of chromate‐based pre‐treatments. This work evaluates the behaviour of cerium as corrosion inhibitor in methacrylate silane‐based hybrid films containing SiO₂ nano‐particles on AA2024. Hybrid films were deposited on aluminium alloy AA2024 by means of dip‐coating technique. Two different types of coating were applied: a non‐inhibited film consisting of two layers (non‐inhibited system) and a similar film doped with cerium nitrate in an intermediate layer (inhibited system). The film thickness was 5 µm for the non‐inhibited system and 8 µm for the inhibited system. Film morphology and composition were investigated by means of GDOES (glow discharge optical emission spectroscopy). Moreover, GDOES qualitative composition profiles were recorded in order to investigate Ce content in the hybrid films as a function of immersion time in 0.05 M NaCl solution. The electrochemical behaviour of the hybrid films was studied in the same electrolyte by means of EIS technique (electrochemical impedance spectroscopy). Electrochemical measurements provide evidence that the inhibited system containing cerium displays recovery of electrochemical properties. This behaviour is not observed for the non‐inhibited coating. GDOES measurements provide evidence that the behaviour of inhibited system can be related to migration of Ce species to the substrate/coating interface. Copyright © 2010 John Wiley & Sons, Ltd.     

铝合金表面改性对有机涂层附着力的影响及腐蚀防护性能研究

利用电化学阻抗（EIS）、扫描微参比技术（SRET）、接触角、粗糙度、附着力、盐雾等测试方法,研究了铝合金阳极氧化与贻贝黏附蛋白（MAP）/CeO₂/硅烷γ-APS（MCA）表面复合修饰的腐蚀防护性能以及对改性聚氨酯涂层附着力和耐蚀性的影响。结果表明,MCA复合膜可抑制铝合金的腐蚀,并具有一定的自修复功能;阳极氧化和MCA表面复合修饰可为铝合金提供有效的早期腐蚀防护作用,且能提高铝合金表面粗糙度和润湿性,显著提升改性聚氨酯涂层在铝合金表面的附着力和耐蚀性,因而结合改性聚氨酯涂层和表面复合修饰可实现对铝合金长期有效的腐蚀防护。     

Effect of Aluminum Alloy Surface Modification on Adhesion of the Modified Polyurethane Coating and Its Corrosion Protective Performance北大核心CSCD

The ordinary organic coatings on aluminum alloy usually encounter a problem of low adhesion to the substrate, which results in destruction and failure of the long-term protective performance of the anticorrosion systems. The surface modification of aluminum alloy is able to enhance the adhesion of organic coating on aluminum alloys, and to improve their protective performance. In this work, a combined surface modification of anodic oxidation and mussel adhesion protein/CeO2/3-aminopropyltriethoxysilane composite film (MCA) was developed on the aluminum alloy. The adhesion of modified polyurethane coated on the treated aluminum alloy and its corrosion protective performance were evaluated comprehensively by using contact angle, adhesion strength, electrochemical impedance spectroscopy (EIS), and scanning reference electrode technique (SRET). The measurements of EIS and SRET demonstrated that the MCA composite film on anodic oxidized Al possessed self-healing function and provided effective protection against early corrosion of aluminum alloy. The pull-off test showed that both anodic oxidation treatment and MCA composite film modification were able to increase the adhesion of modified polyurethane coating on aluminum alloy, and their combined action were supposed to remarkably enhance the adhesion strength up to 17.1 MPa. The reason for the improvement of adhesion was that the anodic oxidation treatment and MCA composite film modification could improve the surface roughness of aluminum alloy, and enhance the surface wettability and surface polarity, which is beneficent to enhance the bonding of the modified polyurethane coating to aluminum alloy surface. The EIS results showed that no any corrosion occurred for the modified polyurethane coating on the treated aluminum alloy during 65 d immersion in 3.5wt.% NaCl solution. The impedance value in low frequency range of the modified polyurethane coating always maintained at a high order of magnitude on the aluminum alloy treated by anodic oxidation and MCA composite film modification, showing an excellent protective performance of the coating system. The evaluation of Neutral Salt Spray (NSS) indicated that the modified polyurethane coating on the treated aluminum alloy owned superior corrosion protection performance, and the adhesion strength remained 13.1 MPa and no any corrosion was found at the scratch locations even after 1200 h of salt spray testing. It was concluded that combination of anodic oxidation and MCA composite film were capable of significantly improving the adhesion of modified polyurethane coating on aluminum alloy and providing long-term effective corrosion protection for aluminum alloy. © 2021 Authors. All rights reserved.     

Sol-Gel-Derived Hybrid Coatings for Corrosion Protection

The corrosion resistance of sol-gel-derived, organic-inorganic, silica-based hybrid coatings was studied. Hybrid sols were prepared by copolymerizing tetraethylorthosilicate (TEOS) and 3-methacryloxypropyltrimethoxysilane (MPS) with a two-step acid-catalyst process. Hybrid coatings were dip-coated on 304 and 316 stainless steel substrates and annealed at 300°C for 30 minutes. The adhesion, flexibility, and biocompatibility of the coatings were examined. Hybrid coatings were found to be relatively dense, uniform and defect free. Electrochemical analyses showed that the coatings provided excellent corrosion protection by forming a physical barrier, which effectively separated the anode from the cathode. In addition, further experimental results revealed that the corrosion patterns are strongly dependent on the nature of the stainless steel substrates. Some possible mechanisms for corrosion breakdown associated with each type of substrate are also introduced.     

Corrosion studies and interfacial bonding of urea/poly(dimethylsiloxane) sol/gel hydrophobic coatings on AA 2024 aluminum alloy

Bis[(ureapropyl)triethoxysilane] bis(propyl)-terminated-polydimethylsiloxane 1000 (PDMSU), an organic-inorganic hybrid, diluted in either EtOH or a mixture of EtOH-PrOH, was used in thin film form (<200 nm) to inhibit the corrosion of AA 2024 alloy. Potentiodynamic, time-dependent cyclovoltammetric measurements and salt spray tests showed that the corrosion inhibition of the latter was 10 times higher than that of the former films. This was correlated with the higher degree of hydrolysis and the formation of more open polyhedral silsesquioxane species (T2) in the bulk heat-treated PDMSU/EtOH-PrOH xerogels (29Si NMR spectra). The structure of the coatings deposited on AA 2024 Al alloy was deduced from the infrared reflection-absorption (IR RA) spectra, which revealed more extensive urea-urea interactions and more efficient silane-Al interface bonding for the PDMSU/EtOH-PrOH coatings with higher corrosion inhibition. Ex situ IR RA potentiodynamic spectroelectrochemical measurements of PDMSU coatings revealed that their degradation did not proceed via the formation of silanol groups and consequent hydration of the coatings but that they decomposed above E(corr) by forming fragments composed of -CH2- segments in an all-trans conformation.