Silane Coatings Research Articles

Silane Coatings for Corrosion and Microbiologically Influenced Corrosion Resistance of Mild Steel: A Review.

Mild steel continues to be the most extensively used construction material in several industries and constructions. However, corrosion of mild steel in aggressive environments is a major concern. Under the tremendously increasing demand for improving the coatings strategies because of the environmental concerns due to some of the traditional coatings, silane pre-treatments have been emerging as one of the effective solutions, among other strategies. Different approaches, such as adding particles of metal oxide (such as SiO2, ZrO2, Al2O3, TiO2 and CeO2), incorporating plant extracts and impregnating 2D materials into the coatings, have been employed for durable corrosion resistance, including for mitigating enhanced corrosion due to the presence of bacteria. This review discusses the critical mechanistic features of silane coatings such as the role of hydrolysis and condensation in the bonding of silanes with metal surfaces. The factors that influence the performance of the silane coatings for corrosion resistance of mild steel are discussed. In particular, this review provides insight into silane coatings for mitigating microbiologically influenced corrosion (MIC) of mild steel.

Comprehensive Testing of Sulfate Erosion Damage of Concrete Structures and Analysis of Silane Coating Protection Effect.

In order to study the protection performance of silane coating on in-service concrete structures in a sulfate environment, we collect concrete samples in the field to simulate the concrete erosion process by accelerated erosion with wetting–drying cycles. We place the samples into protected, exposed and control groups corresponding to a corrosive environment with silane protection, corrosive environment without protection and general environment for three different service conditions. A combination of ultrasonic velocimetry, CT (Computed Tomography) scan imaging, NMR (Nuclear Magnetic Resonance) pore structure analysis, strength testing and other methods are used to analyze the strength, ultrasonic wave velocity, pore structure and other characteristics of the specimens during sulfate erosion. Based on the test results, the protective effect of silane coating on concrete structures under sulfate attack is quantitatively analyzed, and an index for judging the damage rate of specimens is proposed to quantitatively analyze the protective effect of silane coating. The research results show that the damage of the concrete structure under silane protection in a sulfate-attack environment can be reduced by more than 50%; its integrity damage index and strength damage index are easily affected by the location of local defects, which leads to a decrease in the protection efficiency of the surface silane coating.

Modifications of Textile Materials with Functional Silanes, Liquid Silicone Softeners, and Silicone Rubbers-A Review.

General information concerning different kinds of chemical additives used in the textile industry has been described in this paper. The properties and applications of organofunctional silanes and polysiloxanes (silicones) for chemical and physical modifications of textile materials have been reviewed, with a focus on silicone softeners, silane, and silicones-based superhydrophobic finishes and coatings on textiles composed of silicone elastomers and rubbers. The properties of textile materials modified with silanes and silicones and their practical and potential applications, mainly in the textile industry, have been discussed.

Self-assembled hybrid silane/ZnO coatings for corrosion protection of resorbable magnesium alloy

This study aimed to evaluate the potential of an exclusive hybrid coating, based on a silane network, which was developed by sol-gel technique and embedded with nano ZnO to protect the corrosion of an AZ31 magnesium alloy intended for use as biodegradable implants. The coated substrates were subjected to various characterization techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray (SEM-EDS) analysis, and contact angle measurements. The corrosion resistance of applied coatings were evaluated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electrochemical microscopy (SECM) in a PBS solution at physiological temperatures. The chemical composition of the coatings was examined using X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) was carried out to examine the surface topography of the alloy after the polarization test. The results revealed that these coatings significantly improved the anti-corrosion behavior of AZ31 alloy. It was observed that a mixture of silanes offered superior corrosion protection performance owing to the development of a dense cross-linked layer that developed at the interface between the coating and the substrate. The existence of ZnO nanoparticles further enhanced the protective barrier characteristics of the coatings. The outcomes offer a novel approach to the design of hybrid silane coatings with suitable corrosion resistance for biodegradable Mg alloys used as implants.

Wetting of Superhydrophobic Polylactic Acid Micropillared Patterns.

Superhydrophobic (SH) polylactic acid (PLA) surfaces were previously produced by various methods and used especially in biomedical applications and oil/water separation processes after 2008. However, the wettability of SH-PLA patterns containing micropillars has not been investigated before. In this study, PLA patterns having regular microstructured pillars with 12 different pillar diameters and pillar-to-pillar distances were prepared by hot pressing pre-flattened PLA sheets onto preformed polydimethylsiloxane (PDMS) soft molds having micro-sized pits. PDMS templates were previously prepared by photolithography using SU-8 molds. Apparent, advancing, and receding water contact angle measurements were carried out on the PLA patterns containing micropillars, and the morphology of the patterns was examined by optical and SEM microscopy. The largest contact angle obtained without the surface modification of the pure PLA pattern was 139°. Then, PLA micropatterns were hydrophobized using three types of silanes via chemical vapor deposition method, and SH-PLA patterns were obtained having θs of up to 167°. It was found that the highest θ values could be obtained when PLA pattern samples were coated with a silane containing a fluorine atom in its chemical structure. Washing and service life stability tests were also performed on the coated pattern samples and all of the silane coatings on the PLA patterns were found to be resistant over a 6 month period.

Robust silane self-assembled monolayer coatings on plasma-engineered copper surfaces promoting dropwise condensation

Dropwise condensation is well known to result in better heat transfer performance owing to efficient condensate/droplet removal, which can be harnessed in various industrial heat/mass transfer applications such as power generation and conversion, water harvesting/desalination, and electronics thermal management. The key to enhancing condensation via the dropwise mode is thin low surface energy coatings (<100 nm) with low contact angle hysteresis. Ultrathin (<5 nm) silane self-assembled monolayers (or SAMs) have been widely studied to promote dropwise condensation due to their minimal thermal resistance and scalable integration processes. Such thin coatings typically degrade within an hour during condensation of water vapor. After coating failure, water vapor condensation transitions to the inefficient filmwise mode with poor heat transfer performance. We enhance silane SAM quality and durability during water vapor condensation on copper compared to state-of-the-art silane coatings on metal surfaces. We achieve this via (i) surface polishing to sub-10 nm levels, (ii) pure oxygen plasma surface treatment, and (iii) silane coating integration with the copper substrate in an anhydrous/moisture-free environment. The resulting silane SAM has low contact angle hysteresis (≈20°) and promotes efficient dropwise condensation of water for >360 hours without any visible sign of coating failure/degradation in the absence of non-condensable gases. We further demonstrate enhanced heat transfer performance (≈5-7× increase over filmwise condensation) over an extended period of time. Surface characterization data post-condensation leads us to propose that in the absence of non-condensable gases in the vapor environment, the silane SAM degrades due to reduction and subsequent dissolution of copper oxide at the oligomer-substrate interface. The experiments also indicate that the magnitude of surface subcooling (or condensation rate) affects the rate of coating degradation. This work identifies a pathway to durable dropwise promoter coatings that will enable efficient heat transfer in industrial applications.

Insights into the Mechanical Properties of Ultrathin Perfluoropolyether-Silane Coatings.

Ultrathin perfluoropolyether-silane (PFPE-silane) films offer excellent functionality as antifingerprint coatings for display touchscreens due to their oleophobic, hydrophobic, and good adhesion properties. During smartphone use, PFPE-silane coatings undergo many abrasion cycles which limit the coating lifetime, so a better understanding of how to optimize the film structure for improved mechanical durability is desired. However, the hydrophobic and ultrathin (1-10 nm) nature of PFPE-silane films renders them very difficult to experimentally characterize. In this study, the cohesive fracture energy and elastic modulus, which are directly correlated with hardness and better wear resistance of 3.5 nm-thick PFPE-silane films were, respectively, measured by double cantilever beam testing and atomic force microscopy indentation. Both the cohesive fracture energy and modulus are shown to be highly dependent on the underlying film structure. Both values increase with optimal substrate conditions and a higher number of silane groups in the PFPE-silane precursor. The higher cohesive fracture energy and modulus values are suggested to be the result of the changes in the film chemistry and structure, leading to higher cross-linking density. Therefore, future work on optimizing PFPE-silane film wear resistance should focus on pathways to improve the cross-linking density. Subcritical fracture testing in humid environments reveals that humidity negatively affects the fracture properties of PFPE-silane films.

Polymer functional coatings modified by ZrP‐based composites: Preparation and applications on marine concrete

AbstractThe development of high‐performance coatings for concrete structures is essential to ensure their durability and service life. However, most of the proposed developed strategies suffer from various limitations, especially regarding the wear and biological‐corrosion resistances of the coatings. This work reports a facile and efficient method to prepare effective composite coatings by nano‐modification, in which the intercalated composites play structural and functional roles in the corrosion, wear, and biological‐corrosion resistances. An in situ assembly synthesis was used to prepare the intercalated composites. The composites exhibited an innovative alternating skateboard structure and a functional composition. The silane‐emulsion modified with the composites was prepared and coated on the mortar surface to systematically study its performance at the concrete interface. The results indicate the good dispersion stability of the innovative α‐ZrP composites in the silane emulsion and their significant enhancement of the silane coatings' ability to improve the durability of marine concrete. The mechanisms of performance improved by the prepared composites through their unique lamellar structure and interlamellar silver‐nanoparticle composition were also examined. The prepared composite coating exhibits a new strategic approach to solve problems associated with concrete applications and provides technical guidance for surface protection of marine concrete structures.

Alizarin-functionalized organic-inorganic silane coatings for the development of wearable textile sensors

HypothesisThe broad detection properties of alizarin, not only concerning pH variations but also temperature, glucose and health-like relevant cations alterations, make it a molecule of great scientific interest, particularly for developing multifunctional wearable sensors. ExperimentHerein, the alizarin red S dyestuff is bonded with trimethoxy-[3-(oxiran-2-ylmethoxy)propyl]silane, as a sol–gel precursor, to functionalize cotton fabrics. The chemical and structural properties of both plain and silane-functionalized dyestuffs are investigated in solution and solid-state by several chemical-physical characterization techniques. FindingsThe hybrid dyestuff characterization reveals the epoxy ring-opening of the silica precursor, leading to covalent linkages to the sulfonic group of alizarin, which retains its structure during the sol–gel reaction. The silane-functionalized halochromic dyestuff shows similar halochromic behaviour as its pristine solution in the investigated pH range, thus demonstrating a color shift from yellow to red due to the protonation/deprotonation reversible mechanism of the chromophore. The reversibility and repeatability of pH-sensing properties of treated cotton fabrics are confirmed by diffuse reflectance and CIELAB color space characterizations. Cotton fabric functionalized with alizarin-containing sol–gel coating shows excellent durability of halochromic properties, thus emerging as a versatile platform for stimuli-responsive materials.

Performance Evaluation of Silane in Concrete Bridge Decks Using Transmission X-ray Microscopy

The corrosion of steel reinforcement in concrete structures is a most widespread problem. Silane is commonly used as a surface treatment material to reduce the entry of moisture containing harmful chemicals into the concrete matrix, thereby restricting corrosion. There is not a standard test method to evaluate the long-term performance of such sealers when applied on concrete. Moreover, the literature does not have a definitive conclusion on the performance of silanes. In this work, transmission X-ray microscopy (TXM) and optical imaging were used to investigate the mass transport properties and silane thickness of field samples treated with silane to gain insight into the performance of silane coatings. Quantitative measurements using optical staining techniques showed that the average measured silane thickness for all 14 projects was 2.5 mm. The TXM results revealed that, on average, the samples with silane coatings exhibited 8.5 times less penetration of outside chemicals, at a depth of 2 mm, as compared to uncracked samples without silane coatings. This work shows that silanes are a useful and practical tool to significantly reduce the permeability of in-service concrete and resist corrosion.

Studying the Active Corrosion Inhibition Effect of the Ce3+/2-Mercaptobenzothiazole Loaded NaY Zeolite/Zn-Al LDH Based Containers in a Silane Coating

In the present study, the corrosion protective ability of the sol-gel based composite coatings containing two-different types of the cationic/anionic based inhibitors loaded containers. For this purpose, the NaY zeolite and Zn-Al Layered double hydroxides (LDHs) containers were loaded with Ce3+ cations and 2- mercaptobenzothiazole (MBT) separately. The morphology and composition of the constructed micro/nanocontainers were studied using analytical methods, confirming the successful loading of the inhibitors. In this study, the Ce3+/MBT inhibitors were successfully introduced into the LDH/NaY-based zeolite containers.Results evidenced that the combination of the two inhibitors has a constructive effect on the active protection of the AA2024-T3 sheets. SEM micrographs of the unfilled LDH and stupefaction with MBT show that the prepared LDHs have sheet-like morphology. The addition of single-inhibitor filled containers to the sol-gel hybrid coating, and water-based epoxy coating provided active protection for the AA2024-T3 coated substrate. However, the combination of the filled containers with the inhibitor in the above-mentioned coatings resulted in the improvement of the active protection of the substrate, which confirms the synergy between the particles. The NaY containers loaded with the Ce3+ resulted in a significant increase of the |Z|0.01 Hz of the gel-sol hybrid coatings, which indicates the formation of a stable oxide layer with higher resistance. Whereas the |Z|0.01 Hz of the hybrid sol-gel coatings loaded with LDH-MBT were in the same range as the NaY-Ce loaded coatings, containing NaY-Ce and LDH-MBT, showed the highest |Z|0.01 Hz values that indicate the synergy between the inorganic (Ce3+) and organic (MBT) inhibitors in sol-gel hybrid coatings.

Role of Surface Preparation in Corrosion Resistance Due to Silane Coatings on a Magnesium Alloy.

Coating of an organo-silane (Bis-1,2-(TriethoxySilyl)Ethane (BTSE)) has been observed to improve the corrosion resistance of magnesium alloy AZ91D. Three different types of surface preparations have been employed before condensing the silane coating on to the substrate. Corrosion resistance was investigated using electrochemical impedance spectroscopy (EIS). A specific alkali treatment of the substrate prior to the coating has been found to improve the corrosion resistance of the coated alloy, which has been attributed to the ability of the treatment in facilitating the condensation of a relatively compact siloxane film.

Rapid Microwave-Assisted Synthesis of Organo-Modified Nanostructured Silica Coatings with Tunable Water-Repellence Properties

A simple method to fabricate organo-modified silane coatings for water-repellent surface modification was proposed, by using a microwave sol-gel synthesis of hybrid materials. Low-cost fluorine-free tetraethoxysilane (TEOS) and dodecyltriethoxysilane (DDTES) were used as silane derivatives. The organo-modified silica coatings were prepared by the drop-casting method and were characterized by UV-VIS, FTIR spectroscopy, and AFM and SEM microscopy. The morphology of the film show the existence of submicrometer scale roughness due to the aggregation of modified silica nanoparticles. Contact angles of water and diiodomethane on surfaces modified with as prepared nanostructured film were determined in order to assess the hydrophobic and oleophobic properties. The TEOS/DDTES ratio was proved to be a crucial factor in tuning the wettability properties. The results suggest that significant increase of hydrophobicity could be achieved by using non-fluorinated cost-effective silica nanomaterials produced with a rapid ecofriendly method.

The Effect of the Corrosion Medium on Silane Coatings Deposited on Titanium Grade 2 and Titanium Alloy Ti13Nb13Zr.

The present paper focuses on the fabrication of coatings based on vinyltrimethoxysilane and the influence of various corrosion media on the coatings produced. Coatings were deposited on two substrate materials, namely, titanium Grade 2 and titanium alloy Ti13Nb13Zr, by immersion in a solution containing vinyltrimethoxysilane, anhydrous ethyl alcohol, acetic acid and distilled water. The obtained coatings were characterized in terms of surface morphology, adhesion to the substrate and corrosion resistance. As corrosion solutions, four different simulated physiological fluids, which differed in the contents of individual ions, and a 1 mol dm−3 NaBr solution were used. The chloride ions contained in the simulated physiological fluids did not lead to pitting corrosion of titanium Grade 2 and titanium alloy Ti13Nb13Zr. This investigation shows that titanium undergoes pitting corrosion in a bromide ion medium. It is demonstrated that the investigated coatings slow down corrosion processes in all corrosion media examined.

Performance of Ti/Zr and silane coating pretreatments on adhesive bonding of an automotive aluminium alloy produced using the Hot Form Quench (HFQ®) process

Surface pretreatments of an automotive aluminium alloy delivered in F temper and subsequently processed using Hot Form Quench (HFQ®), a novel press forming technique combining solution heat treatment, press forming and in-die quenching to produce high-strength aluminium alloys, for adhesive bonding have been explored. The performance of two commercial pretreatments including Ti/Zr and silane coatings, with either acid spray or alkaline immersion cleaning, was investigated. Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) were employed to characterize the surface chemistry and topography of the alloy after pretreatments. Adhesively bonded aluminium-aluminium single lap shear joints and double cantilever beam specimens were tested to evaluate the performance of the pretreatments on the bonding strength and fracture resistance, respectively. The FTIR and TEM techniques show that the natural oxides and near-surface deformed layer have been successfully removed, but the surface cleanliness level was sensitive to the cleaning approach adopted. New Ti/Zr oxide layers or silane films have been built upon the aluminium surfaces, which confirms that sound surface conditions for adhesive bonding can be obtained for parts produced using HFQ® from F temper input material.

The Influence of the Type of Electrolyte in the Modifying Solution on the Protective Properties of Vinyltrimethoysilane/Ethanol-Based Coatings Formed on Stainless Steel X20Cr13.

The paper reports the results of the examination of the protective properties of silane coatings based on vinyltrimethoxysilane (VTMS) and ethanol (EtOH), doped with the following electrolytes: acetic acid (AcOH), lithium perchlorate LiClO4, sulphuric acid (VI) H2SO4 and ammonia NH3. The coatings were deposited on stainless steel X20Cr13 by the sol–gel dip-coating method. The obtained VTMS/EtOH/Electrolyte coatings were characterized in terms of corrosion resistance, surface morphology and adhesion to the steel substrate. Corrosion tests were conducted in sulphate media acidified up to pH = 2 with and without chloride ions Cl−, respectively. The effectiveness of corrosion protection was determined using potentiometric curves. It has been demonstrated that the coatings under study slow down the processes of corrosion of the steel substrate, thus effectively protecting it against corrosion.

Application of L-citrulline loaded beta-cyclodextrin nano-carrier for fabrication of a corrosion protective silane film on mild-steel

In the present work, a beta-cyclodextrin (β-CD) container was utilized for encapsulating the L-citrulline (L-Cit) molecules to achieve promising active and/or passive protection properties in a silane coating. The inclusion complexes (β-CD-L-Cit) were characterized by Fourier-transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), Raman, and Ultraviolet-visible spectroscopy (UV–Vis) techniques. The morphologies of the particles were visualized by field-emission scanning electron microscopy (FE-SEM). The TGA curves displayed about 6% L-Cit molecules encapsulation via β-CDs. The results obtained from the polarization and electrochemical impedance spectroscopy (EIS) tests results evidenced a mixed inhibition mechanism of the encapsulated inhibitor with an inhibition efficiency of 87% for the β-CD-L-Cit sample.The active protection ability of the silane coating (SiC) was evidenced by the EIS results of the scratched coatings. The total resistance of the β-CD-L-Cit/SiC scratched composite was improved from 5540 Ω.cm2 (neat scratched SiC) to 33,128 Ω.cm2 (scratched SiC + 1 wt% inclusion complexes) corresponding to the coverage of the scratched parts via a barrier film. The FE-SEM micrographs demonstrated the development of a smooth and compact inhibitive layer on the scratched region. Additionally, the conducted EIS test over the intact sample illustrated that the highest anti-corrosion property belonged to the β-CD-L-Cit/SiC sample (88,774 Ω.cm2). The improvements are attributed to the SiC matrix pathways blockage by the β-CD-L-Cit inclusion complexes. Besides the experiments, various modeling and simulation explorations were conducted employing Density Functional Theory (DFT-D), Molecular Dynamics (MD), and Monte Carlo (MC)-based tools for elucidating fundamental understandings about L-Cit and β-CD-L-Cit interactions/adsorption at their interface with metallic adsorbent. These theoretical evaluations strongly reflected the affinity of pure and β-CD complexes of L-Cit onto the adsorbent.

Experimental, Analytical and Numerical Studies of Interfacial Bonding Properties between Silane-Coated Steel Fibres and Mortar

A systematic investigation of the effects of silane coatings on steel fibre–mortar interfacial bond properties was conducted, combining pullout tests, analytical solutions, and meso-scale FE simulations. Nine silane coatings were tested, and their effects were evaluated by 30 single fibre pullout tests. They were found to increase the peak force and energy consumption up to 5.75 times and 2.48 times, respectively. Closed-form analytical solutions for pullout load, displacement, and interfacial stress distribution during the whole pullout process were derived based on a tri-linear bond-slip model, whose parameters were calibrated against the pullout tests. Finally, the calibrated bond-slip models were used to simulate the pullout tests and complex failure of multi-fibre specimens in mesoscale finite element models. Such an approach of combining pullout tests, analytical solutions, and mesoscale modelling provides a reliable way to investigate the effects of fibre–mortar interfacial properties on the mechanical behaviour of steel fibre reinforced concrete members in terms of structural strength, stiffness, ductility, and failure mechanisms.

Improved in-vitro corrosion performance of titanium using a duplex system of plasma electrolytic oxidation and graphene oxide incorporated silane coatings

In this study, pure and 0.1 wt% graphene oxide (GO) incorporated silane layers were deposited on plasma electrolytic oxidation coated titanium as biocompatible sealants using the sol-gel method. Thereafter, their corrosion protection performance was investigated during 14-day in-vitro immersion. The characterization revealed that the silane layers with amorphous structure covered surficial inherent defects of plasma electrolytic oxidation coated titanium and decreased surface roughness as well as hydrophilicity. Further, the embedment of GO nanosheets improved the integrity of the silane layer and caused a reduction in work of adhesion and surface free energy. Accordingly, the chemical affinity and dissolution kinetics of plasma electrolytic oxidation coated titanium in simulated body fluid (SBF) weakened such that the polarization resistance rose to 956.33 and 2213.69 k Ω ·cm 2 after applying pure and GO incorporated silane layers, respectively. The electrochemical impedance spectroscopy demonstrated that the pure silane layer promoted the stability of the plasma electrolytic oxidation coated titanium from about 3 to 7 days. Also, the GO incorporated silane layer provided better stability to the end of 14 days and its protective performance was higher in the first 3 days. The SBF immersion test clarified that the bioactivity of the silane layers was higher than that of titanium due to the induction of particulate calcium-phosphate precipitations. • The surface roughness and hydrophilicity reduced by preparing PEO-Silane-GO. • The in-vitro corrosion stability of PEO-Silane-GO promoted upon 14 days. • The precipitated calcium-phosphate on the duplex coating system increased slightly.

Investigation of composite silane emulsion modified by in-situ functionalized graphene oxide for cement-based materials

Silane coatings were ubiquitously utilized to protect the structure concrete against water and aggressive ions in marine environment. In this paper, a novel design method for silane-based nanocomposite is proposed to enhance the water repellence for silane coatings. The graphene oxide sheets (GO) were first functionalized by in-situ polymerization of dopamine (DA), and then isobutyltriethoxysilane emulsion coatings were fabricated by sol–gel method with incorporation of rGO-PDA. The PDA molecules, bridging the GO sheets and silane molecules by forming chemical bonds of –NH, CO-NH, and Si-O-C, construct amorphous and dense network structure in the emulsion. The laser particle size analysis shows that GO sheets modified by PDA were dispersed better in silane emulsion. Furthermore, the newly developed silane emulsions were sprayed on the concrete surface, while the water and ions resistance were tested to evaluate the effectiveness of coating materials. The silane emulsions modified by rGO-PDA generate higher hydrophobic effects on concrete surface. The surface contact angles can reach as high as 140° and the capillary absorption rate for water is reduced by 90%. In particular, as the rGO-PDA content is 0.2%, the modified silane emulsions exhibit the highest hydrophobicity. Additionally, the long-term sulfate attack and chloride penetration tests also confirm that as compared with coating without modification, rGO-PDA modified silane emulsions can effectively reduce transport rate of chloride and sulphate ion in concrete by nearly 70%, and alleviate concrete degradation in great extent. This paper presents new ideas for the research of nano-modification of composite silane coatings and provides technical guidance for the surface protection against concrete structures in marine regions.