Hybrid Sol Gel Films Research Articles

Pulsed electrophoretic deposition of hybrid coatings from aqueous suspensions as surface functionalization and sealing technique of anodized AA2024. Part I: Morphological characterization, analysis of the interfacial interactions, and evaluation of pore impregnation of the anodic layer

In this two-part series, pulsed direct current for cathodic electrophoretic deposition (pulsed-CEPD) was studied as sealing technique of anodized AA2024 by depositing hybrid sol-gel films from aqueous suspensions. The coating was obtained using tetraethyl orthosilicate and hexadecyltrimethoxysilane as precursors and two pulse widths were used: 10 microseconds and 100 milliseconds. For comparison, continuous direct current for cathodic electrophoretic deposition was also performed. In this first article, it was developed a low-cost automated apparatus capable of creating pulsed fields using a commercial power supply. This was necessary since the automation system provided by the power supply manufacturer did not have a short enough response time able to create pulse widths in the order of microseconds. Field emission scanning electron microscopy (FESEM) and focused ion beam milling techniques were utilized to evaluate the surface morphology and interaction mechanisms in the interface anodic layer/film. Low voltage scanning transmission electron microscopy (STEM)-in-FESEM, and transmission electron microscopy (TEM) were used to evaluate the pore impregnation provided by pulsed-CEPD. Results demonstrated that the developed apparatus successfully created pulsed fields. FESEM micrographs of the anodic layer sealed by pulsed-CEPD showed that the shortest pulse provided the best films, likely due to the greater control of hydrogen bubbles generation and the promotion of a more regular deposition. Also, they revealed two interfacial interactions between the anodic layer and the film. STEM-in-FESEM images showed that the shortest pulse width provided greater pore impregnation by particles. This observation was confirmed by TEM, which demonstrated an incomplete pore impregnation for the longest pulse. Discussion regarding result interpretations is presented based on the generation and dissipation of H2(g) (considering the current interruption); on an alternative to the colloidal stability theory due to the presence of a pulsed field; and on the electrokinetic effects at the electrodes during pulsed-CEPD, that discusses how electroosmotic flow influences the deposition.

Towards facile fabrication of photonics components from inorganic and hybrid sol-gel films. Preparation and optical properties characterization

New trends towards development of integrated optics and miniaturization of photonic devices require fabrication of miniaturized photonic components. Fabrication of waveguiding films with designed optical properties is a fundamental process for production of planar integrated devices.We report here preparation of thin layers based on TiO2 precursor (TET – titanium(IV) ethoxide) and SiO2 precursors, namely inorganic (TEOS – tetraethyl orthosilicate) or organically modified (GLYMO − 3-glycidoxypropyltrimethoxysilane) as candidates for potential application in the planar integrated circuits.The thin layers were deposited on soda-lime glass substrates using the sol-gel method and dip-coating technique and processed at relatively low temperature (up to 300 °C). Several parameters e.g. a) the type of SiO2 precursor, b) the presence of complexing agent for TET and c) heat treatment temperature were tested for their influence on thickness and refractive index of the obtained films.Furthermore, a few series of sol-gel films activated with luminescent dye (Rhodamine B) was fabricated. The influence of the above-listed parameters on luminescent properties of the films was characterized because of lack of systematic study in the literature in this aspect. Moreover, a spectrum of the light at the output of a chosen luminescent dye-doped waveguiding film excited by laser source was investigated.In addition, the subject of our investigations were films prepared at 200 °C with various amounts of TET and organically modified SiO2 precursor in concentration range not presented before. Their optical properties such as homogeneity and values of optical band gap of TiO2 clusters were explored. For selected samples the waveguide properties including the optical losses were evaluated. For the first time, hybrid films with presented composition and refractive index in range of 1.59–1.71 were used for patterning by nanoimprint technique allowing for reproduction of periodic structures, which may serve for example as grating couplers or DFB (distributed feedback) resonators.

Scaling inhibition by sol-gel phosphosilicate hybrid films: Influence of doping Cu2+ and Zn2+ cations

In this work, the scaling protection performance of Zn2+ and Cu2+, added to a phosphosilicate hybrid sol-gel coating and applied on both carbon and stainless steel surface, was evaluated for the first time in a solution containing initially 200 mg.L−1 of Ca2+ (corresponding to a water hardness of 50 °F) at 30 °C. Inhibition efficiency was estimated using chronoamperometry (CA) and quartz crystal microbalance (QCM). Results showed that these smart coatings were efficient to protect steel surface against scaling phenomenon. The coatings containing the Cu2+ inhibitor was the most effective of the systems tested. Moreover, CA and QCM measurements showed that the formation of calcium carbonate deposition on carbon steel decreased when the amount of zinc and copper ions added to the sol-gel film increased. Scanning electronic microscopy and X-ray diffraction results indicated that both cations included in the sol-gel film affected calcium carbonate nucleation by changing the morphology of CaCO3 crystals.

Hybrid Sol-Gel Coatings Doped with Non-Toxic Corrosion Inhibitors for Corrosion Protection on AZ61 Magnesium Alloy.

Physiological human fluid is a natural corrosive environment and can lead to serious corrosion and mechanical damages to light Mg–Al alloys used in prosthetics for biomedical applications. In this work, organic–inorganic hybrid coatings doped with various environmentally friendly and non-toxic corrosion inhibitors have been prepared by the sol-gel process for the corrosion protection of AZ61 magnesium alloys. Effectiveness has been evaluated by pH measurements, optical microscopy, and SEM during a standard corrosion test in a Hanks’ Balanced Salt Solution. The results showed that the addition of an inhibitor to the sol-gel coating can improve significantly the corrosion performance, being an excellent barrier for the L-cysteine-doped hybrid sol-gel films. The incorporation of TiO2 nanoparticles, 2-Aminopyridine and quinine organic molecules slowed down the corrosion rate of the Mg–Al alloy. Graphene oxide seemed to have the same response to corrosion as the hybrid sol-gel coating without inhibitors.

Sol–gel hybrid films based on organosilanes with long alkyl chains

In this paper, we report the synthesis of different silica materials via the acid-catalyzed sol–gel process at room temperature (25°C), using silane precursors with various alkyl chains (dimethyl, octyl and/or hexadecyl), in order to obtain thin films with anti-reflective and hydrophobic properties. Chemical, optical and structural properties of obtained silica materials were thoroughly characterized with various techniques such as FTIR and UV–Vis spectroscopy, AFM analysis, ellipsometric measurements, ESEM and TEM microscopy. Wettability of thin films was evaluated by water contact angle measurements. FTIR spectra of silica materials revealed that the intensity of the Si–O–Si characteristic bands varies depending on the precursor type. From AFM results, we found that the obtained films present a different microstructure as a function of the silica sol formulations. The hydrophobic character of the thin films increases with increasing the length of the hydrophobic chains following the order: dimethyl < octyl < hexadecyl. UV–Vis analysis of the coatings covered with silica materials presents a low reflectance (15.5%). The proposed method in this work has the potential to be a low-cost processing path of nanostructured anti-reflection transparent substrates.

Enhancing the Corrosion Protection of AA2024-T3 Alloy by Surface Treatments Based on Piperazine-Modified Hybrid Sol–Gel Films

The aim of this study was to develop new chrome-free surface pretreatments for AA2024-T3 aluminum alloy. These pretreatments were based on hybrid organic–inorganic sol–gel thin films prepared from mixtures of γ-methacryloxypropyltrimethoxysilane (MAPTMS) and tetramethylorthosilicate (TMOS). Different MAPTMS/TMOS molar ratios were used for optimizing the physical–chemical characteristics of the sol–gel films. The formulation of a set of these sols was modified by incorporating piperazine (1,4-diazacyclohexane) as a corrosion inhibitor. The resulting sol–gel films were characterized by using Fourier transform infrared spectroscopy (FTIR), liquid-state 29Si nuclear magnetic resonance spectroscopy (29Si-NMR) and viscosity measurements. The corrosion performance of the sol–gel films was analyzed by using electrochemical impedance spectroscopy (EIS) and local electrochemical impedance mapping (LEIM). The characterization techniques indicated that piperazine behaved as a catalyst for the condensation reaction during the formation of the MAPTMS/TMOS organopolysiloxane network and produces an increase of the crosslinking degree of the sol–gel films. EIS and LEIM results showed that piperazine is an effective corrosion inhibitor, which can be used to enhance the active corrosion protection performance of sol–gel films.

Effect of Sol-Gel Film on the Corrosion Resistance of Low Carbon Steel Plate

To improve the corrosion resistance on Q235 low carbon steel, in this paper, tetraethyl orthosilicate (TEOS), N-dodecyl trimethoxysilane and γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH560) were used to make organic-inorganic hybrid sol-gel film. Cross cut test adhesion method, neutral salt spray test, electrochemical test and film protective efficiency were taken to value the corrosion resistance property. The corrosion topography was studied by optical microscope. In addition, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) curves and equivalent electric circuit fitting were used to analyze the corrosion mechanism. The cross cut adhesion of sol-gel film can reach 1 class and the protection class can attain 5 class after 72 hours neutral salt spray test. According to the potentiodynamic polarization curve analysis, the corrosion potential of sol-gel film coating sample after 0.5 hours immersion was -0.46 V (vs. SCE) on the 0.1 Hz, and its corrosion current density was 4.74×10-7 A·cm-2. The corrosion potential of bare Q235 low carbon steel plate after 0.5 hours immersion was -0.78 V (vs. SCE) on the 0.1 Hz, and its corrosion current density was 4.75×10-6 A·cm-2. The impedance value on 0.1 Hz (|Z|0.1Hz) (1.27×106 Ω·cm2) of sol-gel film coating sample was more than three orders of magnitude higher than the value of the low carbon steel plate. Even dipping in 3.5 wt. % NaCl for 72 hours, the |Z|0.1Hz value of sol-gel coating sample was still one order of magnitude higher than the low carbon steel plate with 0.5 hours immersion. Sol-gel film with excellent adhesion can significantly improve the corrosion resistance of low carbon steel plate. Sol-gel film can increase the protection efficiency of low carbon steel plate by 90%.

Hybrid sol–gel coatings doped with cerium nanocontainers for active corrosion protection of AA2024

This work presents a new approach to develop protective pre-treatment for AA2024 based on the inhibitor efficiency of cerium ions which are considered as a promising alternative to replace chromate compounds. The inhibition properties of cerium salts for improving the anti-corrosion performance of AA2024 have been characterized by polarization curves and EIS measurements. Cerium ions were inserted into nanoclays platelets by cationic-exchange reactions (CeMMT). XRD analysis proved the presence of cerium ions intercalated into clay structure. EIS measurements and polarization curves highlighted a high corrosion inhibition effect of cerium-modified nanoclays. This effectiveness can be related to the release of 60% of cerium ions from CeMMT structure in sodium chloride as determined by UV–vis measurements. Salt spray test made on scratched sol–gel samples indicated a self-healing effect of cerium ions which provide an active corrosion protection to aluminum substrate. EIS measurements revealed that hybrid sol–gel films doped with CeMMT improve barrier properties and anticorrosion protection of aluminum 2024 substrate.

Influence of radical photoinitiator content on UV curing process and UV-cured hybrid sol–gel films

Hybrid sol–gel coatings are widely used as protective layers for aluminum alloys because of their barrier abilities. This study aims at explaining the barrier properties of a sol–gel coating based on alkyltrimethoxysilane and methacrylate resin by its film structure. This approach was examined by modifying one photopolymerization parameter, e.g., by varying the content of radical photoinitiator. By neutral salt spray test and electrochemical impedance spectroscopy, the barrier properties are highlighted. The film structure is related to thermomechanical properties of films whose glass transition temperature and elastic modulus are measured by dynamic mechanical analysis and nanoindentation, respectively. On a finer scale, conversion of methacrylate functions calculated from Fourier transform infrared spectroscopy has given information on the chemical structure of films. The morphology of these coatings is studied by scanning electron microscopy, transmission electron microscopy, atomic force microscopy operating in tapping mode, and X-ray diffraction. Results revealed that formulations containing between 3 and 9 wt% of radical photoinitiator exhibit the maximal conversion of methacrylate functions and, at a microscopic scale, a homogeneous coating where the two organic and inorganic networks are well interpenetrated. This hybrid sol–gel microstructure corresponds to the highest glass transition temperature and the highest mechanical characteristics (elastic modulus, E and hardness, H) and the highest protection performance. This results in the best barrier properties, and thus the highest corrosion resistance.

Enhanced Antibacterial Capability and Corrosion Resistance of Ti6Al4V Implant Coated with ZrO2/Organosilica Nanocomposite Sol-Gel Films

Ti6Al4V is one of the most commonly used biomaterials in orthopedic applications due to its interesting mechanical properties, corrosion resistance and reasonable biocompatibility, which derive from a compact, thin, and chemically stable oxide film that spontaneously develops on these materials surface able to minimize ion release. Despite these advantages, a post-operative serious and unresolved problem leading to the failure of the implant is the appearance of implant-associated infections. For this reason, the ability to control microbial adhesion is of importance in healthcare, particularly in modern surgery where postoperative implant associated infections are still an unresolved and serious complication. As a proof of concept, we have assessed the antibacterial behaviour of Ti6Al4V surfaces modified by organic-inorganic hybrid sol-gel films with different loading of ZrO2 nanoparticles. The starting organosilica sol was prepared using a mixture of γ-methacryloxypropyltrimethoxysilane (MAPTMS) and tetramethyl orthosilicate (TMOS). Tetrabutoxyzirconium (TBZ) was used as precursor of ZrO2 nanoparticles. Sol-gel films with variable contents of TBZ (0.2—1.0 wt.%) have been tested. The thermal stability of the resulting sol-gel films was studied by using thermal analysis (TG/DTG). Structural characterization of the films was carried out using Attenuated Total Reflectance Fourier transformer Infrared spectroscopy (ATR-FTIR). Surface morphology and composition of coated samples have been analized by Optical and Scanning Electron Microscopy coupled with Energy Dispersive X-ray (OM and SEM/EDX) both before and after the corrosion tests were carried out. The evaluation of the barrier properties on the films and corrosion behaviour of the Ti6Al4V were carried out using Global and Local Electrochemical Impedance Spectroscopy (EIS/LEIS) during immersion in a simulated body fluid (SBF). Regarding bacterial adhesion, two representative strains of the vast majority of nosocomial infections related to orthopedic implants, i.e., Staphylococcus aureus and Staphylococcus epidermidis, were used. Optical and scanning electron microscopies observations have shown the formation of a uniform, homogeneous, crack free and highly adherent protective film on the Ti6Al4V substrates. The electrochemical studies and bacterial adhesion assessments have shown that the incorporation of ZrO2 in MAPTMS/TMOS matrix of the sol-gel films enhance their corrosion protection behaviour and antibacterial capability. Studies on the optimization of the sol-gel formulation to obtain the films with the best antibacterial capability without compromising their good corrosion resistance using different ZrO2 doses are in progress. Acknowledgments The authors would like to acknowledge financial support from the Ministry of Economy of Spain (MAT2015-65445-C2-1-R and MAT2015-63974-C4-3 Projects). M-ERA.NET PCIN-2016-146; Spanish “Junta de Extremadura” and FEDER for the projects IB16117, TE-0016-18 and GR15089

Application of novel sol–gel composites on magnesium alloy

Abstract Application of defect-free, adherent, and corrosion protective sol–gel film on the magnesium alloys is generally difficult. In this study, two novel sol–gel/conversion coating composites were successfully deposited on AM60B magnesium alloy in order to provide sufficient protection against the corrosion. The first composite (Ti–Zr/hybrid) was obtained via combination of a hybrid sol–gel film (synthesized by mixing tetraethoxysilane (TEOS), and 3-glycidyloxypropyl-trimethoxysilane (GPTMS)) as outer layer and Ti–Zr conversion coating as primer. Also, the second composite (Ti–Zr/PTMS) was applied in a similar manner by combination of phenyl-trimethoxysilane (PTMS) sol–gel film with the Ti–Zr conversion coating. The morphology and elemental composition of the Ti–Zr conversion film were assessed by the Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS), respectively. A cracky conversion film was applied on the alloy surface after immersion in the Ti–Zr conversion coating bath which was mainly composed of MgO, TiO2, ZrO2, and MgF2 compounds. Uniform, but not-adherent PTMS and hybrid sol–gel films (pure sol–gel films) with obvious defects were directly deposited onto the magnesium alloy without the Ti–Zr pretreatment which were morphologically characterized by the SEM. However, formation of relatively uniform and completely defect-free Ti–Zr/hybrid and Ti–Zr/PTMS composites after using the Ti–Zr conversion coating as pretreatment was revealed by the SEM observations. In addition, the defects of the Ti–Zr conversion coating were completely filled by the sol–gel layers. The Ti–Zr/PTMS and Ti–Zr/hybrid composite coatings were provided much better corrosion protection capacity than the pure PTMS and hybrid sol–gel films, respectively which was confirmed by the Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP) examinations in 0.05 M NaCl solution.

Hybrid sol-gel coating incorporated with TiO2 nanosheets and anti-corrosive effects on AA2024-T3

Purpose This paper aims to improve the anti-corrosive properties of aluminum alloy AA2024-T3 by coating of hybrid sol-gel coating incorporated with TiO2 nanosheets and to investigate the effect of nanosheets’ size on the improvement of corrosion-resistant performance. Design/methodology/approach A series of hybrid sol-gel films incorporated with varying amounts of TiO2 nanosheets were developed to enhance the corrosion protection performance of the bare metal. Scanning electron microscopy, transmission electron microscopy and atomic force microscopy were used to investigate the structure and morphology of the coatings obtained. In addition, the corrosion-resistant properties of the coatings were evaluated using salt spray test and electrochemical impedance spectroscopy. Findings The corrosion current was as low as 9.55 × 10-4 µA/cm2 and optimal positive corrosion potential reached −0.6 V when the size and loading amount of TiO2 nanosheet were optimized, resulting in a remarkable improvement in anti-corrosive properties. Originality/value This work first investigates the effect of incorporation of TiO2 nanoparticles on hybrid sol-gel coating on the improvement of anti-corrosive performance of aluminum alloy AA2024-T3.

Hydrophobic surface treatments for improving the corrosion resistance of anodized AA2024-T3 alloys

The present study investigates the use of hydrophobic sealing treatments to improve the corrosion resistance of anodized aluminium alloys. Alternative hydrophobic processes to the hydrothermal sealing were tested. One is based on a monocarboxylic acid, myristic acid, and others involve the deposition of hybrid sol-gel film. The samples characterization was performed by Field Emission Scanning Microscopy. The hydrophobic properties were assessed by contact angle measurements, and Electrochemical Impedance Spectroscopy was used to study the anticorrosive properties. All the hydrophobic treatments improved the corrosion resistance of the anodized samples with respect to the hydrothermal treatment. The best results were obtained using the hybrid sol-gel film, where high impedance values are measured after long immersion periods in a 0.1 M NaCl solution. Especially good behaviour was observed in samples sealed with the sol-gel film when the sol was previously heated at 70 °C. This temperature was necessary to dissolve the aggregates that formed at room temperature, which contribute to a more efficient sealing.

Fabrication of large scale PS monolayer colloidal crystal film by using a novel secondary self-assembly method for nanoimprint technique

PS microspheres emulsions with different PS diameters of 207 and 378 nm were prepared by using an emulsifier-free polymerization method. A novel secondary self-assembly method which combined the spin coating and the lifting-up method was used to prepare the close-packed PS MCC films. During the process, the PS MCC film was firstly assembled on a glass substrate by a spin coating technique. Secondly, the obtained PS MCC film was transferred on the air-water interface by immersing the PS glass substrate in water using a dip-coater. Thirdly, the floating close-packed PS MCC films on the air-water interface was transferred to a new glass substrate by using a lifting-up method. During the spin-coating and the self-assembly process, some SDS solution was added in the PS films to improve the uniformity of the PS layer. Effects of the spin-coating speeds, the SDS solution concentration and the lifting-up rates on the morphology of PS MCC films have been discussed. Scanning electron microscopy was used to observe the morphological properties of the PS colloidal crystal films. Results indicate that a relatively close-packed and large scale PS MCC films can be obtained when the spinning speed is 2000 rpm for 60 s, the SDS solution concentration is 2 wt% and the lifting-up rate is 2 mm/min. Furthermore, the polydimethylsiloxane soft mold was replicated from the-fabricated PS MCC films and was then imprinted onto the photosensitive hybrid film under UV-irradiation and thus the micro-lens arrays built in the photosensitive hybrid sol–gel film were obtained.

Stress Gradient Determination in Anti-Corrosion Multilayer Coating

To reduce maintenance and to increase the corrosion protection and lifetime of maritimestructures while complying with environmental standards, multilayer coatings are applied to protectsteel sections. A new generation of hybrid sol-gel and/or HiPIMS Ni-based thin films appear toconstitute an efficient pre-treatment before the anti-corrosion paint application. However, increasingthe number of coatings and associated interfaces may lead to coating failure due to stresses inducedby the different deposition processes. Therefore developing smart models to assess the stressdistribution along these multilayers appears of significant importance. The well-known Stoneyformula cannot be used for multilayers and owing to the large dimensions of the object to be protected.To assess an easily measurable curvature after deposition, thin steel sheets are used but do not respectany more the Stoney hypotheses. So we set up an analytical thermo-elasto-plastic model to evaluatethe stresses induced by depositions in each layer. This model is based on the various thermalexpansion coefficients of every coat. After extrapolation along the complete thickness, combiningsol-gel and PVD deposition smoothens the stress difference between steel and paint. The shearstresses at interface seems thus to be reduced. The evolution of the stress difference between layerswith the imposed deflection can predict the mechanical strength and the interface failure. In order toevaluate the quality of the model, in-situ four-point bending in SEM was performed to study of theadhesion between the various layers. The results deduced from the model are in good agreement withSEM images.

Electrochemical investigations of the corrosion resistance of a hybrid sol–gel film containing green corrosion inhibitor-encapsulated nanocontainers

Abstract In the present study, the effect of Nettle loaded nanocontainers (Nettle-NCs) on the active corrosion inhibition properties of a silane bi-layer coating was studied. In addition, the synergistic inhibition between the Nettle-NCs and zinc acetate (ZA) was studied. Results obtained from electrochemical impedance spectroscopy (EIS) test demonstrated the effective synergistic corrosion inhibition of mild steel by silane coating containing Nettle-NCs and ZA. The active performance of Nettle-NCs/Silane bi-layer coatings on the MS panels was studied by electrochemical impedance spectroscopy (EIS) and salt spray tests.

Free-standing coating patterns fabricated by ultraviolet contact lithography using photosensitive sol-gel coatings

Photosensitive ZrO2-SiO2 hybrid sol-gel coatings containing large contents of chelating rings were prepared by using the zirconium n-butoxide (TBOZ) and methyltriethoxysilane (MTES) as hybrid precursors, and benzoylacetone (BZAC) as chelating agent. The change of ultraviolet (UV) absorption spectra, chemical composition, and optical properties of ZrO2-SiO2 hybrid sol-gel coatings were analyzed before and after UV exposure and calcination. The refractive index of the ZrO2-SiO2 hybrid gel coatings decreased from 1.673 to 1.561 with the increase of the molar content of MTES in precursors. The sol-gel coating patterns with the periods of 20.24 μm, 10.11 μm and 3.99 μm on the PAMS substrates were firstly obtained by using the photosensitive ZrO2-SiO2 hybrid sol-gel films as fundamental materials through a process of UV contact lithography with photo masks and etching with ethanol. Finally, the free-standing gel coating patterns supported by copper grids, with the period of 12.70 μm and line width of 4.93 μm, and the period of 14.20 μm and line width of 3.82 μm, were obtained by removing the PAMS thermal degradation sacrifice layer after being calcined at 330 °C. Micrometer-periodic free-standing gel coating patterns with different structure have potential applications in the laser physical experiments.

Structural characterization and barrier properties of hybrid sol-gel films applied on tinplate

Several hybrid sol-gel formulations applied on tinplate were studied. The organic precursor was vinyltrimethoxysilane (VTMS) and the inorganic one was tetraethylorthosilane (TEOS). The characterization was performed by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) and Fourier Transform Infrared Spectroscopy (FTIR). The optimization of the curing parameters was made by kinetics analysis based on Differential Scanning Calorimetry (DSC) measurements. The barrier properties were evaluated by Electrochemical Impedance Spectroscopy (EIS) technique.The results indicated that only sol-gel solutions with high inorganic precursor ratios are able to form a continuous film, necessary to provide good barrier properties. Thus, tinplate coated with 25% VTMS and 75% TEOS formulation exhibited the better protection properties in the studied medium.

In Situ Formation of Decavanadate-Intercalated Layered Double Hydroxide Films on AA2024 and their Anti-Corrosive Properties when Combined with Hybrid Sol Gel Films.

A layered double hydroxide (LDH) film was formed in situ on aluminum alloy 2024 through a urea hydrolysis method, and a decavanadate-intercalated LDH (LDH-V) film fabricated through the dip coating method. The microstructural and morphological characteristics were investigated by scanning electron microscopy (SEM). The corrosion-resistant performance was analyzed by electrochemical impedance spectroscopy (EIS), scanning electrochemical microscopy (SECM), and a salt-spray test (SST).The SEM results showed that a complete and defect-free surface was formed on the LDH-VS film. The anticorrosion results revealed that the LDH-VS film had better corrosion-resistant properties than the LDH-S film, especially long-term corrosion resistance. The mechanism of corrosion protection was proposed to consist of the self-healing effect of the decavanadate intercalation and the shielding effect of the sol-gel film.

Hybrid Coatings Enriched with Tetraethoxysilane for Corrosion Mitigation of Hot-Dip Galvanized Steel in Chloride Contaminated Simulated Concrete Pore Solutions.

Hybrid sol-gel coatings, named U(X):TEOS, based on ureasilicate matrices (U(X)) enriched with tetraethoxysilane (TEOS), were synthesized. The influence of TEOS addition was studied on both the structure of the hybrid sol-gel films as well as on the electrochemical properties. The effect of TEOS on the structure of the hybrid sol-gel films was investigated by solid state Nuclear Magnetic Resonance. The dielectric properties of the different materials were investigated by electrochemical impedance spectroscopy. The corrosion behavior of the hybrid coatings on HDGS was studied in chloride-contaminated simulated concrete pore solutions (SCPS) by polarization resistance measurements. The roughness of the HDGS coated with hybrids was also characterized by atomic force microscopy. The structural characterization of the hybrid materials proved the effective reaction between Jeffamine® and 3-isocyanate propyltriethoxysilane (ICPTES) and indicated that the addition of TEOS does not seem to affect the organic structure or to increase the degree of condensation of the hybrid materials. Despite the apparent lack of influence on the hybrids architecture, the polarization resistance measurements confirmed that TEOS addition improves the corrosion resistance of the hybrid coatings (U(X):TEOS) in chloride-contaminated SCPS when compared to samples prepared without any TEOS (U(X)). This behavior could be related to the decrease in roughness of the hybrid coatings (due TEOS addition) and to the different metal coating interaction resulting from the increase of the inorganic component in the hybrid matrix.