Silane coating has been used as a steel surface treatment for the promotion of adhesion between a substrate and an organic coating. However, the corrosion protection properties of this coating are not sufficient. Incorporation of various additives and nano-fillers into the coating is a promising way to improve the coating barrier action. In this paper a new nano-filler based on graphene oxide is recommended for this type of coating. The graphene oxide is silanized in the first step through a sol–gel route by using aminopropyl triethoxysilane (ATPES). Then, it is employed in a hybrid silane coating based on the mixture of aminopropyl triethoxysilane and tetraethyl orthosilicate (TEOS). The graphene oxide functionalization was characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The silane coatings filled with silanized and untreated graphene oxide were also characterized by FT-IR, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results obtained from different characterizations showed successful silanization and dispersion of graphene oxide in the silane hybrid coating. The silane coating containing silanized graphene oxide showed superior corrosion protective performance compared to the unfilled silane coating in electrochemical impedance spectroscopy (EIS) and polarization measurements, indicating the considerable corrosion barrier effect of this nano-filler.

Hybrid silane coating reinforced with silanized graphene oxide nanosheets with improved corrosion protective performance

Fundamentals of ceramic powder processing and synthesis

The corrosion process is a major source of metallic material degradation, particularly in aggressive environments, such as marine ones. Corrosion progression affects the service life of a given metallic structure, which may end in structural failure, leakage, product loss and environmental pollution linked to large financial costs. According to NACE, the annual cost of corrosion worldwide was estimated, in 2016, to be around 3%-4% of the world's gross domestic product. Therefore, the use of methodologies for corrosion mitigation are extremely important. The approaches used can be passive or active. A passive approach is preventive and may be achieved by emplacing a barrier layer, such as a coating that hinders the contact of the metallic substrate with the aggressive environment. An active approach is generally employed when the corrosion is set in. That seeks to reduce the corrosion rate when the protective barrier is already damaged and the aggressive species (i.e., corrosive agents) are in contact with the metallic substrate. In this case, this is more a remediation methodology than a preventive action, such as the use of coatings. The sol-gel synthesis process, over the past few decades, gained remarkable importance in diverse areas of application. Sol-gel allows the combination of inorganic and organic materials in a single-phase and has led to the development of organic-inorganic hybrid (OIH) coatings for several applications, including for corrosion mitigation. This manuscript succinctly reviews the fundamentals of sol-gel concepts and the parameters that influence the processing techniques. The state-of-the-art of the OIH sol-gel coatings reported in the last few years for corrosion protection, are also assessed. Lastly, a brief perspective on the limitations, standing challenges and future perspectives of the field are critically discussed.

https://www.mdpi.com/2073-4360/12/3/689/pdf

Hybrid Sol-gel Coatings for Corrosion Mitigation: A Critical Review.

Corrosion Inhibition Performance and Healing Ability of a Hybrid Silane Coating in the Presence of Praseodymium (III) Cations

Electroless codeposition of GO incorporated silane nanocomposite coating onto AZ91 Mg alloy: Effect of GO content on its morphology, mechanical and corrosion protection properties

Transparent and homogeneous hybrid aminopropyl silane-based coatings on steel were prepared by the sol–gel method using hydrolyzed γ-APS as a precursor. The coatings were fabricated by dip coating, and the effect of pH, water/silane ratio and solvent/silane ratio during the coating process was investigated with respect to thermal stability, coating thickness, roughness, contact angle and abrasion resistance. The thickness of the coatings was controlled by the preparation conditions as well as the viscosity of the sols and varied between 0.17 and 4.1 μm. The coatings were in general smooth and the roughness was in the order of a few nanometer. The coatings possessed hydrophilic character with contact angles of water from 65 to 80°, while organic pentadecane wetted the coatings. The abrasion resistance improved with decreasing pH of the water used during hydrolysis of the silane. The abrasion resistant properties of the coatings were characterized with respect to delamination and smearing. Thicker coatings were delaminated while thinner coatings were smeared and displayed lubricating properties. The coatings were thermally stable up to 350 °C, and also displayed a low pore volume and a low surface area.

/pdf/synthesis-and-characterization-of-hybrid-aminopropyl-silane-1io45ldl4f.pdf

Synthesis and characterization of hybrid aminopropyl silane-based coatings on stainless steel substrates

Thin coatings applied to metals is a material-saving process to improve the surface properties such as abrasion and corrosion resistance of the substrate. Pure inorganic coatings are generally too thin to offer long-term protection, and thick coatings are prone to crack formation during processing. However, by incorporating an organic moiety, thicker and more flexible coatings can be developed. Hence sols and coatings based on 3-(aminopropyl)triethoxysilane, γ-APS, have been synthesized as part of the PhD work.Initially, pure inorganic alkoxide-based silica coatings were fabricated. These coatings displayed poor abrasion resistance and were poor alternatives with respect to corrosion protection of carbon steel. The need for thicker coatings was thus proposed, and hybrid inorganic-organic coatings were suggested as a probable solution. Thus in Paper I, hybrid inorganicorganic γ-APS-based sols were synthesized and characterized. Molar ratios of water (or solvent) and silane ratios and sol hydrolysis pH were varied. 29Si NMR was used to study the hydrolysis and condensation reactions. The kinetic mechanisms of the hydrolysis and condensation of the sols showed a difference in the structures formed depending on the water/silane ratio and the sol pH. Increasing the water/silane ratio promoted a faster condensation reaction as evidenced by the early evolution of more condensed species. Reducing the sol pH enabled the condensation reaction to slow down thus fascilitating a more complete hydrolysis reaction. Furthermore, hypostoichiometric sols were shown to consist of linear structures while stoichiometric and hyperstoichiometric sols were more cross-linked as evidenced by the higher viscosity and the combination of T2 and T3 species detected by 29Si NMR.In Paper II, coatings were fabricated from the sols described in Paper I. Transparent and homogeneous hybrid aminopropyl silane-based coatings on steel were prepared by the sol-gel method using the hydrolyzed γ-APS sols as precursors. The coatings were fabricated by dip coating, and the effect of pH, water/silane ratio and solvent/silane ratio during the coating process was investigated with respect to thermal stability, coating thickness, roughness, porosity, contact angle and abrasion resistance. The thickness of the coatings varied between 0.17 and 4.1 μm and was controlled by the preparation conditions of the sol as well as the viscosity of the sols. The coatings were in general smooth and the roughness in the order of a few nanometers. The contact angles with water of the coatings varied from 60 to 80° Organic pentadecane was shown to wet the coatings, which suggested that the coatings also displayed hydrophobic properties. The abrasion resistance improved with decreasing pH of the water used during hydrolysis of the silane. The coatings were characterized with respect to delamination and smearing. Thicker coatings were delaminated while thinner coatings were smeared and displayed lubricating properties. Gels of the hybrid aminopropyl silane-based sols were thermally stable up to 350°C, and the gels displayed a low pore volume and a low surface area.In Paper III, hybrid aminopropyl silane-based sols with a variation in the molar ratios of water and silane, the molar ratios of solvent and silane and pH, were applied as a bond coat to carbon steel substrates. Fracture strength, abrasion resistance and electrochemical polarization studies have been conducted on these bond coats. Furthermore, the bond coats were applied a top coat consisting of a polyaspartic paint, and the combination coatings were subsequently exposed to an ageing resistance test for 5 weeks. The bond coat-top coat combination coatings were demonstrated to significantly improve the corrosion protection behavior of carbon steel. The thickness of the bond coats varied from 0.35 to 4.1 μm, while the bond coat-top coat combination coatings were all in the range of 100 μm.

Hybrid Aminopropyl Silane-based Coatings on Steel

Thin coatings applied to metals is a material-saving process to improve the surface properties such as abrasion and corrosion resistance of the substrate Pure inorganic coatings are generally too thin to offer long-term protection, and thick coatings are prone to crack formation during processing However, by incorporating an organic moiety, thicker and more flexible coatings can be developed Hence sols and coatings based on 3-(aminopropyl)triethoxysilane, γ-APS, have been synthesized as part of the PhD workInitially, pure inorganic alkoxide-based silica coatings were fabricated These coatings displayed poor abrasion resistance and were poor alternatives with respect to corrosion protection of carbon steel The need for thicker coatings was thus proposed, and hybrid inorganic-organic coatings were suggested as a probable solution Thus in Paper I, hybrid inorganicorganic γ-APS-based sols were synthesized and characterized Molar ratios of water (or solvent) and silane ratios and sol hydrolysis pH were varied 29Si NMR was used to study the hydrolysis and condensation reactions The kinetic mechanisms of the hydrolysis and condensation of the sols showed a difference in the structures formed depending on the water/silane ratio and the sol pH Increasing the water/silane ratio promoted a faster condensation reaction as evidenced by the early evolution of more condensed species Reducing the sol pH enabled the condensation reaction to slow down thus fascilitating a more complete hydrolysis reaction Furthermore, hypostoichiometric sols were shown to consist of linear structures while stoichiometric and hyperstoichiometric sols were more cross-linked as evidenced by the higher viscosity and the combination of T2 and T3 species detected by 29Si NMRIn Paper II, coatings were fabricated from the sols described in Paper I Transparent and homogeneous hybrid aminopropyl silane-based coatings on steel were prepared by the sol-gel method using the hydrolyzed γ-APS sols as precursors The coatings were fabricated by dip coating, and the effect of pH, water/silane ratio and solvent/silane ratio during the coating process was investigated with respect to thermal stability, coating thickness, roughness, porosity, contact angle and abrasion resistance The thickness of the coatings varied between 017 and 41 μm and was controlled by the preparation conditions of the sol as well as the viscosity of the sols The coatings were in general smooth and the roughness in the order of a few nanometers The contact angles with water of the coatings varied from 60 to 80° Organic pentadecane was shown to wet the coatings, which suggested that the coatings also displayed hydrophobic properties The abrasion resistance improved with decreasing pH of the water used during hydrolysis of the silane The coatings were characterized with respect to delamination and smearing Thicker coatings were delaminated while thinner coatings were smeared and displayed lubricating properties Gels of the hybrid aminopropyl silane-based sols were thermally stable up to 350°C, and the gels displayed a low pore volume and a low surface areaIn Paper III, hybrid aminopropyl silane-based sols with a variation in the molar ratios of water and silane, the molar ratios of solvent and silane and pH, were applied as a bond coat to carbon steel substrates Fracture strength, abrasion resistance and electrochemical polarization studies have been conducted on these bond coats Furthermore, the bond coats were applied a top coat consisting of a polyaspartic paint, and the combination coatings were subsequently exposed to an ageing resistance test for 5 weeks The bond coat-top coat combination coatings were demonstrated to significantly improve the corrosion protection behavior of carbon steel The thickness of the bond coats varied from 035 to 41 μm, while the bond coat-top coat combination coatings were all in the range of 100 μm

Sidsel Meli Hanetho

Papers

Synthesis and characterization of hybrid aminopropyl silane-based coatings on stainless steel substrates

Hybrid Aminopropyl Silane-based Coatings on Steel

Paraffin wax deposition studies on coated and non-coated steel surfaces