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In anti-corrosion construction, hand-laid fiberglass is commonly used. Although there are many types of fiberglass, epoxy fiberglass remains the most widely used one, and the hand-laying method is the most common way of applying it. The shrinkage rate of epoxy fiberglass is the lowest among the three thermosetting resins—phenolic, epoxy, and unsaturated polyester—thereby ensuring the quality of the hand-laid method. Epoxy fiberglass has good resistance to acids, alkalis, solvents, and most molds. It exhibits excellent corrosion resistance, especially in alkaline environments, and is also heat-resistant. To meet the corrosion resistance requirements in complex conditions, epoxy resins can be blended with other resins to achieve optimal properties (such as epoxy phenol-formaldehyde, epoxy furan, etc.). Every master who works with hand-laid fiberglass knows the three main components of fiberglass: resin, fibers, and curing agent, and epoxy fiberglass is no exception. Commonly used is epoxy resin (E-44, also known as 6101), and the glass fiber used is of the \"three-no\" type – that is, alkali-free, untwisted, wax-free plain-weave glass fiber cloth. Of course, in acidic environments, it is better to use medium-alkali glass fiber cloth, with T31 as the curing agent. Other additives such as powders and diluents are described in the following processes. A high-quality anti-corrosion project relies on both construction techniques and materials; as the saying goes, three parts are the materials and seven parts are the construction. Therefore, the key to hand-laid epoxy fiberglass-reinforced plastic lies in the hand-laying process. Substrate treatment. Most hand-laid fiberglass-reinforced plastics are fabricated on-site. Common substrate materials include concrete and carbon steel, while other substrates are generally rare. To achieve an ideal bond between the substrate and epoxy fiberglass, surface preparation is very important. In addition to being clean at the surface level, a certain degree of roughness is also required. Some suggest that a grinder can be used for simple polishing of the base layer; however, the author believes that mechanical methods such as sandblasting or shot blasting should be employed for treating the base layer in order to ensure the proper level of roughness, which is key when fabricating epoxy fiberglass-reinforced plastics by hand. The concrete substrate is subjected to shot blasting, while the carbon steel substrate is treated with sandblasting to achieve a grade of Sa2.5 or higher, with a roughness of around 75 microns. The floating dust and impurities on the base layer must be blown away using dry air, and the defective areas of the concrete base layer need to be repaired with putty (using prepared epoxy mixture and quartz powder). Preparation of epoxy resin mixture. E-44 epoxy resin is a semi-solid, viscous gel; it needs to be heated to melt, then cooled to around 40 degrees, and mixed with a diluent before being set aside for use. Heating devices include resistance wire furnaces, induction cookers, etc. The author believes that induction cookers are safe and convenient, as they allow for temperature control. The large iron tank for storing these materials can be made by cutting an abandoned diesel tank in half down the middle (be sure there are no flammable gases or liquids inside the tank at the time of cutting to avoid explosions). The addition of a diluent is intended to reduce the viscosity of the resin compound, thereby facilitating handling and meeting the requirements of the manufacturing process. Inactive diluents evaporate during the curing of the resin compound; this not only results in material waste but also increases the shrinkage rate of the epoxy fiberglass, as well as its porosity, thereby reducing the water resistance of the fiberglass product. Therefore, the diluent is used to prevent the epoxy resin from becoming thick again; after mixing with an explosion-proof mixer, it should be covered and stored in a cool place. When selecting a solvent, products or mixtures with good solvency, low volatility, low toxicity, and a high safety factor should be chosen, such as ethanol mixed with propanol, xylene, etc. During the preparation of the bulk material, the tank containing it must be kept at a safe distance of over 15 meters from the heat source, to prevent volatile gases from catching fire. Base layer substrate. After treatment, the concrete or carbon steel substrate must have a primer applied to it within 4 hours; otherwise, secondary rusting may occur, or new pollutants and moisture from the air can accumulate, which hinders proper bonding between the resin and the substrate and can cause the epoxy fiberglass to separate from the substrate surface. The epoxy primer can be diluted with epoxy resin, using a low concentration to facilitate penetration of the primer into the substrate and enhance the bond between the substrate and the fiberglass. T31 or a new type of cashew shell curing agent is used as the curing agent; ethylenediamine is rarely used these days due to its toxicity to humans. The curing agent and the primer must be mixed evenly, using an electric mixer for mechanical stirring. In the author’s opinion, manual stirring is insufficient and can affect the completeness of curing. The amount of T31 added should range from 15% to 25%, depending on the ambient temperature. The application of the primer should be done using rollers or brushes; before use, the fluff on the rollers must be removed. The coating should be applied evenly in a crosshatch pattern, without any accumulation or sagging. In areas where the substrate is uneven, the primer should be mixed with quartz powder to create an epoxy putty that can be used for filling and leveling. In acidic environments, it is advisable to use barium sulfate powder or other acid-resistant materials. After natural drying and curing for 12 hours, proceed to the next step. Hand-stitched cloth. Alkali-free, untwisted, wax-free glass fiber cloth is available in 1 meter, 0.5 meter, and 0.3 meter lengths; the choice can be made based on the construction equipment or existing conditions. However, based on my extensive experience in construction, I find that 0.3 meter length to be the most convenient. For use in acidic environments, use alkali-resistant glass fiber cloth with a thickness of between 02 and 04; the weave pattern can be 10*10 or 12*12. It should be plain-weave, untwisted, and without edges – cloth with edged sections can create stress during the hand-laying process. Epoxy resin materials with twist are not easily impregnated and are not easy to bend; therefore, the hand-laying method generally uses untwisted fabric. For cutting glass cloth, it is best to use Shanghai Zhang Xiaquan sewing scissors, as they allow for quick cutting and are sharp enough to avoid tearing the fabric. The epoxy resin compound should be more viscous than the base material; this viscosity can be adjusted appropriately using a diluent, so that it is suitable for penetrating the fabric pores. Quartz powder with a particle size of 200 to 300 mesh should be used for adding powder, while barium sulfate powder is appropriate for acidic environments, with an addition amount not exceeding 40%. The amount of T31 curing agent should also vary between 15% and 25% depending on the ambient temperature. Based on personal experience, at a normal temperature of 25 degrees Celsius, the amount of T31 used is 20%. The curing agent and resin must be mixed thoroughly; it is recommended to use an electric mixer for this purpose, with a mixing time of around 10 minutes being sufficient. Use application tools such as bristled brushes, following this sequence: apply adhesive, lay the fabric, smooth it with a brush, then apply more adhesive; the overlap width should be at least 10 CM. If two layers are constructed consecutively, the tile-covering method can be used, laying half of the previous layer’s material on top. The key in this process is to ensure that the adhesive penetrates the fabric openings without accumulating or dripping. Before layering the layers of fabric on top of each other, it is necessary to clean and repair the surface of the upper layer of fabric; it is best to polish it as well. To reduce the shrinkage rate of epoxy fiberglass, it is possible to consider using hand-laid chopped fiber mat as the first layer on the substrate, followed by the application of glass fiber cloth; the method for hand-laying epoxy glass chopped fiber mat is the same as that for glass fiber cloth. If modifying epoxy resins, such as epoxy-phenol, epoxy-furan, epoxy-polyester, etc., the appropriate type can be selected based on its respective properties; however, the amount of the secondary resin added must not exceed 30%. Coating the fabric. Hand-applied fiberglass reinforced plastic coatings serve as a direct barrier against corrosion; therefore, they require a high resin content, and no powder additives are needed. The amount of thinner used should also be appropriate. In the author’s opinion, if it is possible, it is not difficult to apply such coatings without using any thinner. A high solid content is an important indicator of corrosion resistance, and the coating should be applied at least twice, or even more times. The amount of T31 to be used and the precautions associated with it are the same as those mentioned above. The coating should be applied in a crosshatch pattern, ensuring even coverage without any gaps; there should be no dripping or accumulation, no pinholes, and no bubbles. The curing time must be at least 24 hours, with the finished product ready for use only after 10 days, as the resin has not yet fully cured and cross-linked during this period. The longer the curing time, the more complete the curing process will be. If possible, heating can be used to accelerate curing and achieve the best quality for the product.