Applications and Performance of Ethyl Silicate in Protective and Functional Coating Systems

Ethyl Silicate as an Inorganic Surface Treatment for Concrete Durability

The protection of concrete surface from environmental aggressions is often a basic issue for the enhancement of its durability. Due to the unsatisfactory long-term performance of many organic products and the subsequent need for frequent re-application, growing interest has been recently addressed toward inorganic materials. The results so far obtained point ethyl silicate as a promising surface treatment for reinforced concrete protection.  Ethyl silicate can penetrate into concrete and reduces, once hardened, its permeability without any pore occlusion or film forming effect, the other products give multiple surface layers, locally cracked and detached. Ethyl silicate provided the best performance in limiting the water ingress into both concrete types, while the other products were not so effective (or even completely ineffective). In terms of chloride and carbonation resistance, only the application of ethyl silicate and sodium silicate produced a significant improvement and, and in particular, the treatment with ethyl silicate gave the best performance for both short and long time of exposure to chloride and carbon dioxide. [1]

Structural Characteristics and Synthesis Pathways of Ethyl Silicate

Various coatings have been developed for protecting ferrous alloys against corrosion in modern technologies and ethyl silicate polymeric based coatings have additional advantages of shock-resistance, lightweight, and excellent chemical properties comparing to nowadays coatings. Ethyl silicate, often referred to as tetraethoxysilane or tetra ethylortho silicate (TEOS), Si(OC2H5)4, is a tetra functional silicon alkoxide synthesized in two ways; firstly, via reacting ethanol with silicon tetrachloride (SiCl4) and secondly, via reacting ethanol with silicon metal. [2]

Functional Applications of Ethyl Silicate in Coatings and Material Enhancement

Zinc-rich paints based on ethyl silicates combine outstanding, long-term corrosion protection of ferrous surfaces with resistance to high temperatures. The benefits are best seen in aggressive environments where there is exposure to severe weather and chemicals. Typical application areas are bridges, ships and structural steel. Many plastics, like acrylic resin, and polycarbonate resin, have downside that scratches quickly occur on the surface, greatly detracting from the quality of items. However, by utilizing products that use ethyl silicate, a very thin film of SiO2 is created on the surfaces, that resulting in enhances the resistance of abrasion and reduces scratching. Moreover, heat and weather resistance is dramatically enhanced, by using ethyl silicate onto a variety of different substrates, and the fields of application of the substrate are widely extended. Additionally, the light transmission can be boosted and avoid the reflection of the light more operatively by adding it to plastic or glass. Moreover, the particles' surfaces can be covered by a SiO2 membrane, thus enhancing the dispersibility of the particles and other properties. [2][3]

Advantages of Ethyl-Silicate-Based Binders in Inorganic Anti-Corrosion Coatings

Surface coatings based on inorganic binders can be successfully used as primers for the effective protection of steel against corrosion. For the formulation of inorganic coatings, alkali metal silicates such as sodium, potassium and lithium silicates and alkyl silicates such as ethyl silicate are commonly employed as inorganic binders. Ethyl silicate based binders have proved to be superior to alkali metal silicates in overall performance, despite the fact that former ones produce solvent-borne compositions, whereas alkali metal silicate based coatings are water-borne. Ethyl silicate based coating films are self-curable at room temperature in the presence of adequate atmospheric moisture. The final (cured) films of ethyl silicate based coatings are composed mainly of silica, or silica and zinc, if zinc is used as a pigment. Therefore, cured films of ethyl silicate based (inorganic) coatings are considered better, in view of environmental aspects, than organic coatings which invariably produce films composed of organic polymers. The films of these coatings, being silica based, are resistant to temperature up to 400°C, where most organic coating films fail. Further, films of zinc-rich ethyl silicate based coatings protect the substrate (steel) by providing much more effective cathodic protection than that provided by zinc-rich organic coating films. In addition, ethyl silicate based binders react with the iron (substrate) chemically, and hence provide unmatched adhesion to restrict corrosion creepage, if any kind of corrosion at all starts on the substrate. The films, being rock-like hard and quite rough, provide excellent inter-coat adhesion to the subsequent coat. [4]

References:

[1] Franzoni, E., Pigino, B., & Pistolesi, C. (2013). Ethyl silicate for surface protection of concrete: Performance in comparison with other inorganic surface treatments. Cement and Concrete Composites, 44, 69-76.

[2] Ali, M., Mohmmed, J. H., & Zainulabdeen, A. A. (2021). Experimental study of the mechanical and corrosion properties of ethyl silicate resin applied on low carbon steel. Archives of Materials Science and Engineering, 108(2).

[3] https://www.wacker.com/h/medias/7350-EN.pdf?utm

[4] Parashar, G., Srivastava, D., & Kumar, P. (2001). Ethyl silicate binders for high performance coatings. Progress in Organic Coatings, 42(1-2), 1-14.

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