Discuss the characteristics and applications of \"wet-on-wet\" spraying

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Let’s discuss the characteristics and applications of \"wet-on-wet\" spraying. This coating method involves applying one coat of paint, allowing the solvent in the coating film to evaporate to a certain extent, then applying another coat while the film is still wet, and finally drying and curing it all at once. Unlike conventional spraying processes, the \"wet-on-wet\" spraying method features the ability to apply a new coat of paint without having to dry the previous one. This reduces the number of processing steps, saves energy and costs, improves efficiency, and does not require additional investment in equipment or larger production facilities – making it a highly efficient and cost-effective painting method. However, this method also has its limitations; not all coatings can be sprayed using the “wet-on-wet” technique. Because if, after applying one coat of paint, the next coat is applied before the previous one has dried completely, it will affect the drying of the entire coating layer; it may also cause sagging and wrinkling, so this method of spraying should not be used. Coatings suitable for \"wet-on-wet\" spraying include amino resin coatings, vinyl chloride resin coatings, acrylic resin coatings, polyurethane coatings, and epoxy resin coatings. However, their requirements for \"wet-on-wet\" spraying also vary; for example, with amino resin coatings, the next coat can be applied once the previous coating is no longer sticky to the touch, and after being left at room temperature for 15 minutes, it can be placed in an oven for drying. For polyurethane coatings, the solvent in the paint must be almost completely evaporated, and the coating film must be slightly cross-linked but not fully cured before the next coat can be applied. For perchloroethylene resin coatings and thermoplastic acrylic resin coatings, the next coat can be applied 1 hour after spraying. Therefore, when using the \"wet-on-wet\" spraying method, it should be applied flexibly depending on the type of coating in order to achieve the best coating results. Examples include epoxy ester primer / acrylic resin topcoat, epoxy ester primer / metallic flash topcoat, and epoxy ester primer / amino-cure topcoat. When applied using the \"wet-on-wet\" spraying method and then dried with far-infrared radiation, these coatings can cure and form a solid film effectively. In particular, when the epoxy ester primer is used in combination with amino-cure topcoats or metallic flash topcoats, it offers significantly better performance in terms of coating properties, application conditions, and technical and economic costs compared to the traditional \"dry-on-wet\" method. Therefore, the \"wet-on-wet\" spraying technique should be widely promoted.