Commonly used paint types, characteristics, and applications

Applications of coatings (1) Oil-based paints. Can be used as a paint for construction. Rinsed oil can be applied to oilcloth and umbrellas. After being formulated into a thick paint, it can be used directly to fill metal pipe joints with hemp fibers, to create canvas waterproof coatings, and as an inexpensive camouflage coating. Oil-based mixed paint can be used to coat buildings, doors and windows, as well as outdoor ironware and other products. (2) Natural resin paint. It can be used as an internal primer, putty, and topcoat to meet various general requirements. Shellac varnish can be used as a primer for wood. (3) Asphalt paint. Chemical machinery and equipment, pipes, vehicles, chassis, frames, metal roofs, small hardware parts, ship bottoms, fishing nets, battery components, etc., that can be coated for corrosion protection. Oil-based drying varnish can be applied to bicycle frames, sewing machine heads, dashboards, engine cylinders, motors, and insulating materials; it can also be used as soundproofing and sealing material. (4) Phenolic resin paint. Outer walls of painted iron barrel containers, indoor furniture, floors, inner walls of food cans, and ventilator casings. Inner walls of chemical corrosion prevention equipment, metal wire meshes, insulating materials. Polyamide-modified phenolic coatings can replace shellac paints for coating wood and paper. (5) Alkyd resin paint. Used in indoor and outdoor buildings, indoor and outdoor doors and windows, furniture, office equipment, various types of vehicles, structures above the waterline of ships, ship hulls, ship cabins, metal scaffolding for steel structures, bridges, overhead power towers, derricks, construction machinery, mining machinery, radiators, the outer walls of iron tanks, agricultural machinery, cranes, bulldozers, silk-varnish coatings, electrical insulation materials, etc. (6) Amino resin paint. Used for drying coatings in buses, mid-size cars, and bicycles, sewing machines, thermoses, computers, instruments, medical equipment, motor equipment, household appliances, small metal parts, etc. . (7) Nitro paint. Aircraft wing fabric, automobiles, leather, high-quality wood products, pencils, handicrafts, as well as mechanical equipment that requires rapid drying, decorative paints, gold powder preparations, aluminum powder coatings, and more. (8) Perchloroethylene resin paint. Used in aviation, corrosion protection of chemical processing equipment, prevention of wood from spreading flames, moisture and mildew resistance for metals and non-metals; as well as for the exteriors of various machine tools and motors. It is also applicable to the surfaces of concrete, brick, stone, and cement products, and serves as a three-protection coating in humid tropical regions. (9) Acrylic paint. Fabric treatment, artificial leather, metal corrosion protection, can outer walls, paper polishing, high-end wood products, instruments, dials, medical equipment, automobiles, light industrial products, bricks and stones, cement, concrete, brass, aluminum, silverware, etc. for coating; painting of industrial machinery and equipment in humid tropical areas. (10) Polyester paint. It is used for wood, bamboo products, high-end furniture, chemical-resistant equipment, and the surface coating of enameled wire; it can also be used to produce polyester putty with low shrinkage. (11) Polyurethane paint. Used in the chemical industry, ships, outdoor equipment, corrosion-resistant equipment, the interior surfaces of vehicles, oil tanks, tank cars, decks, floors, wooden furniture, the frames and skins of aircraft, vehicles, as well as on surfaces made of wood, leather, plastic, concrete, fabric, paper, aluminum, and tin. It can also be used underwater or in humid environments. (12) Epoxy resin paint. It can be used as a protective coating for various chemical and petroleum equipment, as well as for floors, decks, interior walls of ship cabins, and electroplating tanks. Epoxy coal tar pitch coatings can be used as anti-corrosion coatings for marine structures. (13) Rubber paint. Chemical processing equipment, rubber products, vehicle canopies, internal combustion engine ignition coils, road signs, cement, bricks and stones, flame-retardant materials, outdoor equipment, and industrial equipment for which winter construction conditions do not affect drying. (14) Silicone resin paint. High-temperature resistant mechanical equipment (such as chimneys, boilers, reaction towers, rotary kilns, sintering furnaces), Class H insulation materials, marble resistant to wind erosion, outdoor coatings designed for long-term maintenance, and chemicals-resistant materials, etc. (15) Ethylene resin paint. Waterproof fabrics, as well as peelable coatings for glass, paper, toothpaste tubes, cables; for rust prevention on ship bottoms; for anti-fouling purposes; for fire resistance; and to prevent radioactive contamination. (16) Water-based coatings. Wall coatings for interior and exterior wall painting ； Considering the sound-absorbing effect, a textured ceiling paint can be used for the ceiling ； For indoor cement floors, use 107 or 801 cement-based coating. Latex paint can be applied to doors and windows, walls, fabrics, and paper. (17) Various special coatings. Heat-resistant coatings, fire-retardant coatings, strippable coatings, color-changing coatings, fluorescent coatings, temperature-indicating coatings, glass shatter-resistant coatings, etc. Selection of coating and paint systems: Paint system compatibility refers to the possibility of coordination between the paint layer and the surface it covers, between different paint layers, as well as with the respective application methods, when carrying out painting work. During construction, even with high-quality paint, a clean surface, and advanced techniques, if the compatibility of the paint is neglected, the desired results cannot be achieved. Therefore, when selecting paint, it is essential to carefully choose a suitable paint combination. (1) Select paints with different properties according to the different materials of the surface to be painted. For coating steel surfaces, rust-resistant paints such as red lead rust paint and iron oxide rust paint with good rust prevention properties should be used ； For painted aluminum alloy surfaces, ordinary anti-rust paint cannot be used; instead, zinc-chromate yellow anti-rust paint should be selected ； An oil-based paint should be used as a base coat on the wood surface. For ordinary plastered surfaces, pig’s blood is used as a base coat; on cement surfaces, alkali-resistant latex paint, 106 paint, or vinyl chloride paint should be used. Drying-type paint cannot be used on buildings or large metal objects; paint that dries naturally must be used instead. (2) To enhance the adhesion between coatings, it is also important to pay attention to the compatibility of primers, putties, topcoats, varnishes, and various auxiliary materials; generally, paints using the same type of solvents and thinners should be selected. For example, vinyl chloride primers, vinyl chloride putties, and vinyl chloride topcoats. (3) The painting materials and application methods must be properly matched. For wooden doors and windows coated with oil-based paints, brushing is the more appropriate method; using spraying not only wastes material but also dirties the walls. When applying amino alkyd baking varnish, the \"wet-on-wet\" technique is used (that is, applying a second coat before the first one has fully dried), which improves the adhesion between the coats and allows for the elimination of one baking step. When applying the alkyd primer in combination with the nitro topcoat, using a \"wet-on-wet\" technique can also prevent the phenomenon of the underlying layer being damaged. However, it is important to control the thickness of the primer during application – it should not be applied too thickly. Furthermore, the appropriate time for applying the nitro topcoat also needs to be considered carefully. Water-soluble paints are generally applied using electrophoretic coating. Paints with high viscosity should be applied using high-pressure airless spraying, while two-component paints require a dual-nozzle spray gun. (4) Select appropriate paint materials based on different usage environments and requirements. For the painting of indoor fixtures, aesthetic appearance, wear resistance, and washability are required, while weather resistance is not a necessity. Bathroom walls should be painted with paint that has good waterproof properties, while kitchen walls need to be resistant not only to moisture but also to oil and gas contamination. For various vehicles, bridges, and agricultural machinery, paints with good weather resistance must be used. Matte paint or latex paint can be used for indoor walls. For exterior walls, paint that is resistant to sunlight and aging must be used. As for the coatings for wooden surfaces, most of those used on wooden furniture are transparent varnishes; they are clear and allow the original wood grain to show through. There are also a small amount of opaque colored paints. The coating is required to be matte or glossy, and it should not irritate the eyes when exposed to sunlight; however, it needs to be full and thick. The specific quality requirements are as follows: 1. The varnish should be able to reveal the original patterns of the wood and preserve its aesthetic appearance ； 2. After the coating dries, it should not shrink or crack at low temperatures, and it must not stick back when exposed to higher temperatures ； 3. Water-resistant, wear-resistant, and strong adhesion ； 4. It has a good luster, light color, and excellent light-retaining properties; it can be polished and waxed. Rhinoceros lacquer is generally used for the coating of wooden furniture, floors, and musical instrument surfaces, or as a sealing coat with an oil-based varnish. For ordinary indoor wooden doors and windows as well as standard furniture, relatively inexpensive phenolic varnish is used. For high-end solid wood furniture, violins, pianos, sewing machine tables, radios, and television casings, nitrocellulose wood varnishes with good drying properties and a bright finish, as well as acid-cured amino varnishes, are used. Wear-resistant sports flooring, high-quality wood finishes, and wooden enclosures for instruments are required; polyurethane varnish, unsaturated polyester wood varnish, acrylic wood varnish, etc. should be used. For the selection of surface coatings for light industry and household appliances, as well as metal products, black asphalt-based baking varnishes are still commonly used for sewing machines and bicycles. To improve the thickness of the paint film, reduce the baking temperature, and enhance colors, in addition to synthetic amino baking varnishes, high-solid-content acrylic baking varnishes and oil-free polyester baking varnishes can also be used. Lightweight and compact bicycles often use amino or acrylic metal flash topcoats as well as multi-colored topcoats. For some household appliances such as washing machines, refrigerators, and electric fans, amino baking paint is currently used in most cases. To save energy and protect the environment, catalytic self-drying acrylic polyurethane paints and water-soluble acrylic baking paints are recommended. For the inner walls of certain household appliances, flame-retardant interior coatings should be used ； For household micro motors, odorless motor paint should be used. Toys, stationery, clocks and watches, lighting fixtures, thermoses, etc. must use coatings free from toxic heavy metal pigments such as lead, antimony, chromium, and cadmium. For wind instruments made of steel tubes, acrylic or polyurethane varnishes should be used. For gold and silver jewelry as well as high-end metal decorations, acrylic cathodic electrophoretic varnishes should be employed to prevent discoloration and to stop hydrogen sulfide from causing the silver to corrode and turn black. This paint not only preserves the natural color and texture but also offers a certain degree of corrosion resistance. For coatings on the inner walls of food cans, coatings based primarily on epoxy phenol resins should be used; sometimes, a certain amount of zinc oxide and tin powder is added as well ； For exterior wall coatings, acrylic white primers and topcoats should be used to prevent yellowing under high-temperature cooking conditions. For flexible packaging and aluminum foil packaging, UV-curable coatings should be used. The difference between traditional oil-based paints, oil-based coatings, and modern resin-based paints: Paints that use oils with drying properties as their main film-forming components are called oil-based paints ； Paints that use synthetic resin as the main film-forming substance are called resin paints ； Paints that use oils and a small amount of natural resins as their main film-forming substances are called oil-based paints. These three types of coatings have different properties due to their differing main film-forming substances. Oil-based paints have good resistance to atmospheric conditions; they do not easily crack, flake off, or wear away. They are suitable for use as a primer and topcoat on surfaces both indoors and outdoors. They offer good penetration when applied, and are inexpensive ； The disadvantages are slow drying, a soft film layer, inability to be sanded or polished, and poor resistance to alkalis. Resin paint has good gloss and excellent weather resistance. It has strong adhesion and good adaptability for application; it can be applied either by brushing or spraying ； The disadvantages are that the paint film is soft, has poor water and alkali resistance, and takes a long time to dry. The properties of oil-based paints vary depending on the content of drying oil resins. Oil-based paints with a low oil content dry quickly, have good gloss, are hard and wear-resistant, but they are brittle and not resistant to sunlight ； Oil-based paints with a high oil content yield coatings that are soft, glossy, and have good weather resistance, but they dry more slowly. Oil-based paints with a medium oil content have properties that lie between those of paints with a low oil content and those with a high oil content. Oil paint is a type of paint in which drying oil serves as the main component for forming the film; it is also known as oily paint. Oil-based paints include linseed oil, thick paint, and oil-based mixed paints, etc. Oil-based paints have a flexible film, good adhesion, excellent resistance to atmospheric conditions, are less prone to flaking and cracking, are inexpensive, and are easy to apply. However, oil-based paints dry slowly, have poor mechanical properties, cannot be sanded or polished, and their hardness and gloss are not satisfactory. Refined oil is made from refined drying oils (such as tung oil, linseed oil, catalpa oil, etc.), to which an appropriate amount of solvent and drying agent is added. The coating formed by clear oil is flexible, but dries slowly and has very low hardness; therefore, it can only be used to coat objects with modest quality requirements, serving to provide waterproofing and moisture resistance. Its main uses are: (1) used alone. It can be done by wiping or brushing; wrap cotton in a white cloth to form a cloth ball, or use a paint brush dipped in mineral oil to wipe or brush the surface 1–2 times. If a base color is needed on the wood surface, first mix the pigment into a paste and apply it as a base coat; once it has dried, sand it with fine sandpaper to remove dust, and then apply 1–2 coats of clear varnish. If construction takes place in winter or the drying property decreases due to prolonged storage, an appropriate amount of drying agent can be added to accelerate drying. (2) Modulating thick paint. The amount of cleaning oil used is 20%–40% of the weight of the thick paint; it should be mixed well and then filtered before use. (3) Modulating red lead. The amount of cleaning oil used is 25%–50% of the weight of the red lead powder. During preparation, the red lead powder is gradually added to a small amount of cleaning oil until a thick paste is formed; thereafter, the remaining cleaning oil is added, and after mixing well, the mixture is filtered before use. Thick paint, also known as lead paint, is a type of paint that is inexpensive but of poor quality. It is a paste made from pigments and drying or semi-drying oils. Oil generally accounts for only 10%–20% of the total weight. It cannot be used directly. An appropriate amount of refined tung oil and turpentine must be added to achieve a workable consistency. The typical ratio for formulating a topcoat is 60%–80% thick paint and 20%–40% turpentine, while the ratio for formulating a primer is 70%–80% thick paint and 20%–30% turpentine. An appropriate amount of drying agent must be added in winter to facilitate drying. Paint made with thick paint has properties similar to oil-based mixed paint, but it is cheaper than oil-based mixed paint. However, since the oil components have not been polymerized, a larger amount of pigment is required, and since it needs to be prepared on-site, its quality is generally inferior to that of oil-based paints; it is only suitable for use as a primer or for painting wood, buildings, and wooden boats where high quality standards are not required. Thick paint is usually applied by brushing, with 2–3 coats applied using a brush. Note that the second coat must be applied only after the first coat has fully dried; under normal temperatures, this drying time is around 24 hours. Mixed paint: Mixed paint is the most widely used type by painters; it is an opaque paint that has been properly formulated. But early painters were all *accustomed to mixing their own paints. Therefore, the name “blended paint” is still used. It is made by mixing drying oils with pigments, solvents, drying agents, and other ingredients. If the varnish contains resin, it is called magnetic varnish; however, this is generally limited to a ratio of resin to oil of 1:2 or less. If the amount of resin exceeds this ratio, it is conventionally classified as a type of magnetic paint. Those without resin are called oil-based mixed paints. Oil-based mixed paints are inexpensive, offer good adhesion, and their paint film possesses high elasticity and weather resistance; however, they dry slowly and have poor gloss. They are suitable for use on indoor and outdoor buildings, doors, windows, as well as on outdoor iron and wooden fixtures. Magnetic varnish dries faster than oil-based varnish, and it also has better gloss and hardness compared to oil-based varnish; however, it tends to lose its luster, crack, and flake, making it suitable only for coating indoor wooden items and components. Varnish, commonly known as varnish paint, is a transparent paint without pigments that is often used. Unlike rosin oil, varnish has **superior properties** due to the addition of resins, solvents, and drying agents to the polymerized oil. Varnishes can be classified into short-oil, long-oil, and medium-oil varnishes based on the weight ratio of resin to oil contained in them. The ratio of resin to oil is around 1:1; this type of varnish is known as short-oil varnish. It dries quickly, producing a hard and shiny finish, but it has poor weather resistance and is only suitable for finishing indoor wooden items ； When the ratio of resin to oil is greater than 1:3, it is called long-oil varnish. Its film dries slowly, is elastic, and offers good resistance to atmospheric effects; however, the film is soft and not resistant to abrasion, making it suitable only for coating outdoor wooden items ； If the content of resin and oil is between that of short-oil and long-oil varnishes, it is called medium-oil varnish; its properties lie between those of long-oil and short-oil varnishes, and it can be used on wooden items both indoors and outdoors. Shellac, shellac sheets, and shellac varnish: Shellac is a gum-like substance secreted by lac insects that live on certain plants in tropical and subtropical regions. Due to the presence of many impurities, it needs to be washed to remove pigments and impurities, then ground, heated, dissolved, and filtered. After rolling, it turns into orange-yellow flakes – these are shellac flakes. Flaky shellac cannot be used directly for coating; it must be dissolved in alcohol to turn into a liquid form of shellac varnish, commonly known as turpentine. Shellac varnish is characterized by fast drying time, bright color, a hard and shiny finish, good adhesion, and strong sealing properties; it makes an excellent priming material for wooden products and furniture. Its downside is that it tends to turn white when exposed to water or moisture. Since natural shellac resources cannot meet the demand, synthetic shellac made from resin is now being used; it has superior properties to natural shellac and is being widely promoted for use. Antirust paint: The function of antirust paint is to prevent metals from rusting and to enhance the adhesion of the coating. After the metal is coated with anti-rust paint, its surface is isolated from the atmosphere. The rust inhibitors contained in the anti-rust paint enable the metal surface to become passivated, preventing external harmful substances from undergoing chemical or electrochemical reactions with the metal. The commonly used rust-proof paints include the following: (1) Red lead rust-proof paint. It is an anti-rust primer made by mixing red lead with drying oil. This paint has good penetration and wetting properties, a flexible film, and strong adhesion. Due to its high density, red lead tends to settle; if stored for too long, it becomes thicker, making it difficult to apply, and it dries more slowly with a softer paint film. It is generally used as a base layer for black and white tin sheets. (2) Iron red phenolic anti-rust paint. A thick liquid prepared from rust-inhibiting pigments and long-oil phenolic or ester-based lacquers, to which about 10%–30% by volume of turpentine should be added at the time of use. It has good adhesion of its paint film, and it will not suffer from undercutting caused by the softening of the topcoat; it is used as a primer for spraying to prevent rust. (3) Iron red alkyd anti-rust paint. It is prepared by adding pigments such as iron oxide red and lead chromate yellow, along with fillers, alkyd paint, solvents, and drying agents. It has good adhesion, strong rust resistance, high hardness, elasticity, impact resistance, and strong resistance to nitro compounds; it also exhibits good bonding properties with nitro paints and alkyd paints. It is suitable as an anti-rust primer for ferrous metals, especially before applying nitrocellulose paints and amino alkyd bake-offs; applying this anti-rust primer to the surface prior to baking yields better results. (4) Zinc yellow anti-rust paint. It is prepared by mixing pure phenolic paint with zinc chromate yellow pigment and then grinding it. It has strong adhesion and high resistance to the marine environment, and is used for coating lightweight metal substrates. (5) Gray anti-rust paint. It is made by adding lead-zinc oxide, as the main rust-inhibiting pigment, to the varnish. It possesses excellent rust resistance and resistance to atmospheric erosion, making it suitable for coating outdoor steel components such as high-voltage line frames and iron railings. Since it is oily, it dries slowly. (6) Other anti-rust paints. There are many types of anti-rust paints, including barium metaborate anti-rust paint, zinc ash anti-rust paint, epoxy anti-rust paint, vinyl chloride anti-rust paint, aluminum powder anti-rust paint, mica iron oxide anti-rust paint, and zinc yellow acrylic anti-rust paint. Rust-primer coatings: Currently, in China, rust-primer coatings mainly fall into three categories: stable type, conversion type, and penetrating type. (1) Stable type. Its main function is to inhibit rust, that is, to maintain the current state and prevent further expansion. Its composition is basically an iron red anti-rust primer to which some highly effective corrosion inhibitors are added. However, due to the limited amount added, only a very small amount of rust can be converted. Stable rust-resistant coatings can function on the surfaces of steel equipment with slight rust. (2) Transformative type. It is mainly composed of substances that can convert rust (such as phosphoric acid, organic acids, potassium ferrocyanide, etc.), resins that can form a coating film (such as polyvinyl butyral resin), and solvents (such as ethanol, butanol), etc. Its feature is its ability to convert a certain amount of rust (with a thickness of around 80–100 micrometers). Although its rust-removing capability is greater than that of stable rust-coating materials, its solid content is lower; the thickness of the film it forms is only about half that of the films produced by stable coatings. It also has a drawback in that the conversion solution and the film-forming solution must be stored in separate containers; they are only mixed together in a specific ratio just before use before application. If the mixed paint is not used up, it has to be discarded, resulting in waste. (3) Penetrating type. It does not rely on chemical reactions with rust; instead, it uses a solvent with extremely strong penetration ability to penetrate into the rust through physical diffusion, surrounding the loose and porous rust particles so as to isolate them from the surrounding medium and thereby stabilize the rust. For rust prevention on riveted and threaded areas, penetrative rust-on-coating is the most suitable option. Heavy-duty anti-corrosion coatings: Also known as high-performance anti-corrosion coatings, these coatings are characterized by the use of advanced anti-corrosion materials in combination with zinc-rich primers, as well as thick-formula variants. Coatings provide corrosion protection primarily by using a protective layer to shield the metal from corrosive agents in the environment; for this purpose, coatings should possess the following properties: (1) extremely low permeability to water, oxygen, and corrosive agents ； (2) It has strong adhesion to the primer and is durable ； (3) Appropriate coating formula (including rust-inhibiting pigments and necessary additives) ； (4) Coating thickness ； (5) There is an appropriate coating system. In heavy-duty anti-corrosion coating systems, resins such as epoxy resin, vinyl resin, chlorinated rubber, polyurethane, acrylic resin, and epoxy-tar asphalt are commonly used as base materials. Their respective characteristics are: Epoxy resin: good water resistance, chemical resistance, and adhesion ； Ethylene resin: Dries at low temperatures; has good water resistance, chemical resistance, and weather resistance. Chlorinated rubber: Dries at low temperatures; has low permeability to oxygen and water vapor, as well as good weather resistance. Polyurethane: Dries at low temperatures; has good water resistance, chemical resistance, and weather resistance. Acrylic resin: Has good weather resistance, light resistance, and color retention ； Epoxy-tar asphalt: good water resistance ； In addition to ordinary weather-resistant and chemically resistant pigments, emphasis should be placed on the use of flaky pigments such as aluminum powder, mica, and iron oxide. Combined use of heavy anti-corrosion coatings: (1) Select primers made from rust-inhibiting pigments that can passivate metals or provide cathodic protection (such as red lead, zinc chromate, potassium chromate, and zinc powder). Currently, zinc-rich primers are mostly used in combination. (2) Choose intermediate coat paints with strong adhesion, such as ferrochrome epoxy polyamide intermediate coat paints and acrylic polyurethane intermediate coat paints. (3) Choose topcoats with good weather resistance and decorative properties, such as polyurethane and acrylic topcoats. Intermediate coat: The coat that lies between the primer and the topcoat is called an intermediate coat. In addition to putty as the intermediate coat, there are also general-purpose primers, a second layer of putty, and sealing primers. The function of the intermediate coating is: (1) to protect the primer and putty layers from being worn away by the topcoat ； (2) Increase the adhesion between the primer and topcoat layers ； (3) Has a certain filling capacity to eliminate the roughness of the primer layer (effective for 10-micron roughness) ； (4) Improve the decorative quality of the coating ； (5) Increase the thickness of the coating to improve its decorative and waterproof properties as a whole. To this end, the intermediate coat should be well compatible with the primer and topcoat, and it should also be easy to sand; a smooth surface should be obtained after wet sanding. Intermediate coatings are generally applied using spraying methods and automatic electrostatic spray painting. The second coat is generally applied in two consecutive \"wet-on-wet\" applications, resulting in a dry film thickness of approximately 35–40 micrometers. An intermediate coating is used only in products with high decorative requirements; products with low decorative needs generally do not use an intermediate coating (that is, the topcoat is applied directly onto the primer layer). Sealant Sealants have the following properties: (1) Their durability should be similar to that of the topcoat ； (2) When applied directly to the putty coat, it can fill small pores ； (3) While preventing the formation of pinholes, it reduces the hygroscopicity of the second sizing layer ； (4) Improve the fullness of the painted surface to a certain extent ； (5) It can prevent dulling caused by surface roughness and absorbency ； (6) The topcoat has its own luster, making it easy to detect defects on the paint surface optically ； (7) It has better sandability than the topcoat. Nitro paint, commonly known as spray paint, is based on nitrocellulose, with synthetic resins, plasticizers, and pigments added (paints without varnish contain no pigments). It is formulated by dissolving these components in organic solvents and then grinding them together. The advantages of nitro paint are: (1) rapid drying. Generally, paint takes 24 hours to dry, while nitro paint can dry in just a few minutes. Due to rapid drying, dust does not easily adhere to the surface of the object being coated, which ensures good coating quality. Moreover, no baking equipment is required, which **helps save time during processing and improves work efficiency. Because of the rapid drying, it also saves space at the construction site. (2) The paint film is hard and wear-resistant. Nitro paint possesses excellent mechanical strength; its film is hard and wear-resistant, and it can be waxed and polished. Unlike paint, it does not have drawbacks such as dust accumulation, stickiness, or wrinkling after drying. (3) It has a good luster. The disadvantage of nitro paint is that its coating tends to turn white in humid environments ； Nitro paint has a low solid content, and once it dries and sets, it is not as thick as other types of paint; therefore, 2–3 coats are usually applied during application, while for more intricate projects, as many as 8–9 coats may be needed. Nitro paint also has poor leveling properties, making it difficult to apply with a brush. Amino alkyd paint is a type of high-grade baked paint. It is made by combining amino resin with alkyd resin. As a painting material, the paint film formed by heating and curing pure amino resins is excessively hard and brittle, with poor adhesion. When combined with alkyd resin, it achieves good modification effects: the amino resin improves the hardness, gloss, drying speed, as well as the alkali and oil resistance of the alkyd resin ； Alkyd resins improve the brittleness and adhesion of amino resins. Therefore, the characteristic of amino alkyd paint is that its varnish has a light color ； The paint film has a full appearance and vibrant colors ； The paint film is tough and has strong adhesion ； Good aging resistance of the paint film, as well as resistance to flaking and cracking ； Does not stick back after drying, and does not fall off under impact ； It has good construction properties; the paint film does not wrinkle easily, and it has excellent leveling characteristics ； It possesses considerable resistance to acids, alkalis, water, oil, and wear, as well as good electrical insulation properties ； During construction, it can shorten the drying time, improve production efficiency, and facilitate continuous baking in the painting process. Amino alkyd paint is widely used in agricultural machinery, vehicles, instruments and meters, bicycles, sewing machines, thermoses, medical devices, electrical and mechanical equipment, as well as other small metal objects. Amino alkyd paints generally require baking to form a film. Some people have already adopted the method of adding hydrochloric acid as a curing agent to enable amino paints to dry at room temperature. Thermochromic paint is a special type of paint that indicates changes in the surface temperature of an object through changes in color or shape. There are mainly two categories: one is reversible temperature-indicating coatings. Reversible coatings change color when the coating is heated to a certain temperature, and return to their original state once cooled down. The other category is irreversible coatings. Reversible coatings change color due to chemical reactions when heated, and therefore do not return to their original color. Insulating coating paint: Coating paint is a type of paint applied to the surfaces of motors, electrical devices, windings, etc., that have been impregnated with insulating paint. The surface of an object after being coated with a topcoat is firm and smooth, possessing luster as well as moisture resistance. It also enhances the insulator’s resistance to moisture intrusion and chemical gas corrosion. Commonly used topcoats include: (1) C32‑58 alkyd drying arc-resistant paints in various colors (formerly known as 1322, 1320), with a heat resistance rating of Class E. This paint has a high film strength and is resistant to arcs and oils, but it has poor moisture resistance and dielectric properties; it is suitable for coating motor and electrical coil windings. The drying temperature is 105±2 degrees Celsius, with a duration of 3 hours; xylene can be used as a solvent. (2) C32－39 various colors of alkyd arc-resistant paints (1323, 1321); their heat resistance rating is Class E. Their properties are the same as those of C32－58, but they can dry at room temperature, with a drying time of 24 hours (at 20 degrees Celsius). Suitable for covering motor and electrical appliance coils that cannot be baked at high temperatures, as well as for surface finishing of insulating components in various electrical appliances and instruments. (3) W31-11 silicone drying insulating paint is an H-class insulating paint. It has high heat resistance and insulation properties, as well as good moisture resistance, impact resistance, and dielectric properties, making it suitable for covering electrical coils in high-temperature environments. The drying temperature is 200 degrees Celsius, for about 3 hours. (4) Epoxy ester insulating paint – there are many types of such coating paints, such as H31-3 epoxy ester insulating paint. H31－31 gray epoxy ester insulating paint (Class B); it can cure either by itself or through drying, and is suitable for coating motor and electrical coil windings ； H31－32 gray epoxy ester insulating paint, suitable for coating the surfaces of motors and electrical coil assemblies in humid tropical areas ； H31－54 gray epoxy ester drying insulating paint is a Class B insulating paint with good mildew resistance as well as decent oil and moisture resistance; it is suitable for coating the outer surfaces of electrical motors, appliances, and precision instruments used in humid tropical areas. Insulating impregnating varnish: The main functions of insulating impregnating varnish are to increase the breakdown voltage, thermal conductivity, and to reduce moisture absorption. Applied to the surface of conductors to form an insulating layer, serving an insulating and protective function. Insulating paint that can maintain good thermal strength and dielectric properties at high temperatures is also known as high-temperature (impregnation) insulating paint. Impregnating varnishes are the most widely used; they can be applied to porous insulating materials such as cardboard, gauze, fabrics, etc., as well as motor windings and electrical coils. High-temperature insulating impregnating varnishes can be used to impregnate motors and electrical equipment that operate at high temperatures. Fire-retardant coating: Also known as flame-retardant coating, in addition to the decorative and protective properties common to ordinary coatings, it possesses two additional special properties. One is that the coating itself is non-flammable or difficult to ignite, thereby preventing it from being set on fire by flames ； Secondly, it can prevent combustion and delay its spread; that is, it stops or suppresses the expansion of combustion for a certain period of time, thereby giving people enough time to carry out fire extinguishing efforts. Based on their fire protection principles, fireproof coatings can be divided into two main types: intumescent fireproof coatings and non-intumescent fireproof coatings. At present, the fireproof coatings produced and used in our country are mostly intumescent fireproof coatings. When exposed to fire, this coating expands and forms bubbles, creating a foam-like insulating layer between the combustible material and the source of fire. This layer encloses the material that is being protected, and it also triggers a series of chemical reactions that suppress combustion, thereby preventing the material from burning. Dyes are organic substances that can color fibers or other materials in a quite durable manner. Its chemical composition is complex, with the majority being derivatives of aromatic compounds. Based on their application methods, they are generally classified into acid dyes, alkali dyes, direct dyes, mordant dyes, reduction dyes, sulfide dyes, and reactive dyes – there are many types with various uses. Unlike pigments, dyes have bright colors; they are soluble in water, ethanol, acetone, and other organic solvents, and can color the entire object being dyed ； The pigment is insoluble in the medium and can only color the surface of the object. For example, when using a dye solution to color wood, the solution penetrates into the wood and undergoes complex physical and chemical reactions with its constituent materials (such as cellulose), thereby coloring the wood without covering its grain. There are two types of dyes commonly used in paints: acid dyes and alkali dyes. Acid dyes generally have weak coloring power and produce light colors ； Alkaline dyes have strong coloring power, as well as deep and vivid colors. Solvent: Any volatile liquid used to dissolve film-forming substances such as oils, resins, and cellulose derivatives is called a solvent. The solvent also serves a diluting function. It is a major component of liquid paint. These mainly include: (1) turpentine, (2) terpene oil, (3) benzene, (4) toluene, (5) xylene, (6) ethyl acetate and butyl acetate, (7) ethanol, (8) propanone, (9) cyclohexanone, (10) styrene, gasoline, kerosene, etc. The role of solvents: Solvents are an important component in liquid paint formulations. It is closely related to the manufacturing, storage, and application of coatings, as well as the quality of the paint film. Its functions are as follows: (1) It dissolves and dilutes the film-forming substances in the paint, reducing its viscosity to facilitate application through techniques such as brushing, spraying, dipping, or pouring. (2) Improve the stability of paint storage and prevent the film-forming substances from gelling. At the same time, adding a solvent fills the bucket with solvent vapor, which can reduce skinning on the paint surface. (3) It ensures good leveling of the paint film, preventing defects such as excessive thickness or thinness of the film, as well as brush marks and wrinkling caused by poor painting properties. (4) Adding a solvent to the paint improves the wettability and penetration of the paint on the surface of the object being painted, thereby enhancing the adhesion of the coating. (5) The solvent is a volatile liquid that serves only to dissolve and dilute the film-forming substance; it evaporates into the air as the coating dries, remaining neither in the coating. The difference between solvents and thinners: Both solvents and thinners are liquids used to dissolve substances and reduce the viscosity of coatings; they evaporate continuously as the coating dries. What is the difference between solvents and diluents? (1) Solvents can independently dissolve the film-forming substances in the coating, whereas thinners only serve to dilute; they can only dilute existing solutions and reduce the viscosity of the coating. (2) As a component of paint, the solvent has been added to coating products in a certain proportion ； Diluents are generally added only during the application process, in order to change the viscosity of the paint, improve operational efficiency, or meet the requirements of certain application methods (such as spraying, brushing, etc.). (3) All solvents contained in coatings can serve as diluents, but not all diluents can be used as fluxes. Therefore, we cannot treat “solvents” and “thinner” as the same thing and add them to coatings blindly. (4) Since the same liquid has varying solvating capacities for different film-forming substances, a liquid that is a solvent for one such substance may merely be a diluent for another. The same is true in reverse. In other words, the difference between a solvent and a diluent lies in their ability to dissolve a specified primary film-forming substance. Selection of solvents: Choosing the right solvent is crucial for improving the quality of the coating film, reducing costs, and minimizing potential health risks to operators. Therefore, the following points should be considered when selecting a solvent: (1) When selecting a solvent, its ability to dissolve the substances that form the coating film must be taken into account; adding the solvent should not cause turbidity or precipitation, and the paint should remain transparent while having an appropriate viscosity. (2) The solvent should have a light color; it is best to be colorless and transparent, with as few impurities as possible, as otherwise this will affect the color of the paint film after it dries. (3) Among solvents of the same type, those with low toxicity should be preferred as much as possible. If the use of highly toxic solvents is necessary, consideration should be given to using mixed solvents (replacing part of the highly toxic solvents with less toxic ones) in order to reduce toxicity and enhance workplace safety. (4) The evaporation rate of the solvent must be taken into account to suit the form of the paint film. Too rapid evaporation can affect the leveling of the paint film ； If evaporation is too slow, it causes the paint film to sag and dry slowly. (5) The primer and topcoat of the same type of coating should use the same solvent. (6) Prefer solvents with high flash points, ignition points, and auto-ignition points; at the same time, the solvents should have low corrosivity and good chemical stability. (7) Choose solvents that are relatively inexpensive, suitable for use, widely available, and easy to obtain.