Fluorocarbon coatings are the general name of a series of coatings with fluorine-containing resin as the main film-forming substance. It is a new coating modified and processed on the basis of fluorine-containing resin. Its main feature is that the resin contains a large number of F-C bonds, and the bond energy is 485KJ/mol, ranking first among all chemical bonds. Under the action of heat and light (including ultraviolet rays), F-C is not easy to break, so it shows long weather resistance and chemical medium resistance. This basically determines that it has better performance than other types of coatings, so it is known as the "king of coatings" in the industry. As a high-tech functional coating and a brand-new protective material for surface decoration, its weather resistance, chemical resistance and many other properties are superior to the popular high-grade coatings such as polyurethane, silicone and acrylic resin, and its outdoor service life is as long as 20 years. Fluorine resin has a series of varieties such as room temperature curing and low temperature baking, and has the ability of coating repair and regeneration. The construction method is basically the same as that of general coatings. Fluorine coatings have been widely used in construction, chemistry, electrical and electronic, machinery, aviation, aerospace, household items and other fields. Especially in heavily polluted and corrosive environment, it shows its superior protective performance.
Coating is a widely used engineering material. The coating and the surface of the coated object can form a solid film, which can protect and decorate the coated object, protect the surface of the coated object from the erosion of moisture, chemical gases and microorganisms exposed to the atmosphere, as well as the invasion of sunlight, wind and rain and seawater, and prolong its service life. Therefore, with the development of coating industry, a variety of coatings with excellent functions and performances are continuously developed, which not only beautifies human life, but also makes coatings have different protective functions for coated objects, such as three-proof coatings and temperature-resistant coatings. Because of convenient construction, durability, low cost and wide application range. Therefore, it is widely used in many fields of national economy. In today's colorful world, it is unthinkable without pigments.
The successful development of fluorine coatings is a milestone in the history of human coatings. Its acid and alkali resistance, aging resistance, weather resistance, pollution resistance, self-cleaning, salt spray resistance and antibacterial property are incomparable to any other coating. In particular, the appearance of room temperature curing fluorocarbon paint further expanded its application field and was praised as "the king of coatings" by the coating industry.
As the saying goes, "painting in three parts and building in seven parts" is true. It is necessary not only to ensure the durability of the coating, but also to meet the use requirements of the coated object and give full play to its protection and decoration functions. In addition to the quality of the coating itself, it is also important to adopt appropriate construction technology and drying and curing conditions. Therefore, the most important thing in coating construction is: 1, choose the appropriate coating varieties according to the requirements of coating, 2, adopt different construction techniques and procedures according to different objects to be coated, and 3, consider the relationship between function and construction convenience.
In short, users, especially paint constructors, must carefully study the construction conditions, such as surface treatment of coating materials before painting, selection of construction methods, control of construction conditions, reasonable construction procedures, selection of drying and curing methods, etc. Work out a set of reasonable construction technology. Secondly, it is necessary to choose a suitable coating variety. Small samples must be tested when necessary, and must not be sloppy. The most taboo is to buy a bucket of paint brushes. Often only know to choose a color paint or superstitious foreign paint, can not achieve the expected coating effect.
1. Surface treatment of the painted object: No matter what construction technology is adopted, the surface treatment of the object before painting is a key in the construction process. Therefore, in addition to scale and corrosion, there are pollutants such as oil, moisture and dust on the surface of metal objects, as well as defects such as pits and peeling on the surface, just like other coated surfaces. Therefore, the feeling and impression of the coating surface cannot reach a satisfactory level. Before construction, if it is not completely cleaned, the paint layer will be wrapped and peeled off. Directly affect the adhesion of the coating. Corrosion resistance, decoration and service life. The protective and decorative effects of coatings can not be achieved. Therefore, all kinds of coatings, no matter which construction method is adopted, can not ignore the surface treatment of the substrate.
A. Surface treatment of metals: As far as metals are concerned, there are rust layers, pits, oil stains, welding slag, moisture and some old paint films on the surface before painting. If you paint directly without surface treatment, it will lead to poor appearance of paint film and inherent hidden dangers. For example, the water resistance, oil resistance, acid and alkali resistance of the coating film are reduced, some of them will fall off quickly, and some will gradually produce rust spots, which will reduce the protection and decorative effect of the coating film. Therefore, it is necessary to deal with it properly and not to do it casually.
1. Derusting: including manual derusting, mechanical derusting, sandblasting and chemical derusting. ① Manual derusting: Use emery cloth, scraper, hammer chisel, steel wire brush and other tools to brush off the rust layer by hand, shovel and steel wire brush, then wipe off the rust dust with cotton sand before painting. ② Mechanical derusting: With the help of small motor and pneumatic tools, such as angular grinding wheel and grinder, rust and dirt are removed by impact and grinding. Mechanical derusting has high efficiency and is widely used in construction site. ③ Sand blasting derusting: It is a high-efficiency and good-quality derusting method. A more thorough method of derusting quality can remove impurities and rust layer attached to metal surface. The surface after sandblasting has good mechanical adhesion to the coating. Sand blasting includes dry sand blasting, wet sand blasting, closed dust-free sand blasting, shot blasting and high-pressure water sand blasting. (4) Chemical derusting: immerse ferrous metal in acidic solution. The acid solution reacts chemically with the oxide on the metal surface to achieve the purpose of rust removal. After pickling, the metal surface must be thoroughly washed with water to remove residual acid, then neutralized with 5% sodium carbonate solution or washed with warm water containing 20% Shi Shui, and painted immediately after drying. This method is especially suitable for machining workpieces with complex shapes and structures.
In recent years, rusty coatings have been widely used. That is, if the steel surface is not treated, it will be coated with rusty primer immediately. There are four types of this coating as primer: stable, conversion, penetration and emulsion. However, rusty painting can't be used in any painting project. It depends not only on the quality of the rust bottom itself, but also on different substrates and construction requirements to a great extent. Therefore, rusty coating can only be used for metal workpieces with low requirements for the workpiece to be coated and no thick oxide scale. Can not be used at will, saving labor and time.
2. Dismantle all kinds of equipment. Animal and vegetable oil, mineral oil and vaseline are usually attached to the surface of iron plate of new steel. Cleaning is needed before construction to enhance the adhesion of the coating. The degreasing method is as follows: ① Alkaline solution method: it consists of dilute solutions such as sodium hydroxide, sodium silicate, trisodium phosphate or sodium carbonate. (2) Emulsification method: Emulsifier is dispersed in water with organic solvent, with high oil removal efficiency. However, the chemical reaction between emulsifier residue and paint should be considered, and the actual coating test is generally carried out with emulsion. ③ Solvent method: treating with gasoline, naphtha, trichloroethylene and dichloroethane. Trichloroethylene is a colorless, nonflammable solvent with low boiling point, which has good degreasing effect, high speed, no pollution, liquid can be distilled and recovered, and the utilization rate is high.
3. Phosphating treatment: Phosphating treatment is to use an insoluble and extremely thin crystalline double salt protective film on the surface of steel, which has good rust resistance and adhesion. After phosphating treatment, its biggest advantage is that it can prevent the coating from spreading and expanding when it is damaged locally or under other circumstances. Phosphating treatment is also suitable for aluminum, zinc and other alloy surfaces, but it is mainly used for the surface of steel parts in large-scale assembly line operation. At present, there are many phosphating methods, including chemical phosphating, electrochemical phosphating and jet phosphating. And there is a phosphating primer instead of phosphating.
4. Purification treatment: In order to close the pores of the phosphating layer or generate a thin passivation film on the metal surface, the metal surface is separated from various media at the boundary to achieve good protection effect. After chromate treatment, trivalent and hexavalent chromizing layers can be formed, so the corrosion resistance is good. Pretreatment methods such as degreasing, derusting, phosphating and passivation are only suitable for mild corrosion or new metal painting.
B, wood surface treatment The surface of the coated wood must be dry, and the moisture content is below 7%, so that the coating is not prone to cracking, foaming, film falling and other ills. Before construction, remove the dust on the wood surface, and after preliminary polishing with fine sandpaper, the putty can be scraped off. Putty can be divided into water and oil. After water-based putty is painted, in order to show the waterline, the surface putty can be wiped off with a wet cloth after drying, and the varnish or transparent paint brushed is bright and has natural wood grain patterns. Oily putty is thick. Rough surface is used for filling, so putty should be strong, quick-drying and easy to polish. For pine, rosin must be dissolved first, mixed with 80% alkali solution and 20% acetone aqueous solution, and coated on the coating surface of water-based materials. After 2-3 hours, the saponified resin is removed from the wood surface with hot water or 2% sodium carbonate solution.
C. Surface treatment of cement Generally, the surface of new cement cannot be painted immediately. Because it is very humid, it contains free alkali and salt. Especially in winter construction, adding antifreeze such as calcium chloride, salt or triethylamine into mortar not only increases the free alkali of the wall, but also easily absorbs moisture and increases the water content of the wall. There is lime in the wall material, and carbon dioxide in the air turns it into calcium carbonate. Although it has a certain strength and cohesive force, because there are many single crystalline particles, after absorbing water in the air, the particles expand and contract when they dry, so the wall is easy to lose powder and make the paint fall off after a long time of use. At present, in the construction of exterior wall coatings, a cement exterior wall alkali-resistant primer should be brushed under the condition that the wall surface is dry, or a water-based coating with styrene-acrylic liquid as the main material and penetrant, zinc sulfate and zinc oxide added, and then the surface powder and floating alkali are removed after drying, and then the construction is carried out. In the construction of cement surface, it is best to use epoxy or above alkali-resistant primer or putty mixed with tea-acrylic emulsion, white cement and white powder, so that the wall surface is not only alkali-resistant, but also water-resistant. The construction of cement wall is a special matter, which should be paid special attention to. Because it is generally used for external wall construction, it is best to use epoxy primer for construction. Before use, blow dry the wall with a blowtorch and then apply a primer. It will be more resistant to water after drying.
D. Surface painting of porcelain sintered bricks and Massek, especially the old tile buildings need to be renovated. At present, only oxycarbon paint can guarantee the quality. However, before construction, in addition to solvent cleaning, the parts that have lost porcelain should also be filled with putty, and then the epoxy bottom surface or epoxy zinc yellow primer should be brushed for treatment.
Introduction to various painting methods 1, brush painting method: painting with a brush is the simplest method. Generally, fluorocarbon paint is diluted to a viscosity of 4 cups 10-20 seconds, and then brushed with a soft brush dipped in a little paint. It's best to clean the brush, soak the root of the brush with fluorocarbon paint, dry it and then remove the hair that is easy to fall off. When in use, the part of the brush immersed in the pigment should not exceed one third of the hair length. Then it is applied obliquely first, then straight, first up and then down, first left and then right, and vertically and horizontally to form a uniform thin layer. This operation is light and fast. In case of epoxy primer or acrylic primer, the viscosity should be controlled within the range of 15-25 seconds. Better results can be achieved by using fluorine paint combined with primer.
2. Dip coating method: all the objects to be coated are immersed in a tank filled with paint, and the objects soaked with paint are taken out of the tank in a short time, hung on a fixed shelf, and the redundant paint is allowed to drop naturally and dried to achieve the purpose of painting. Commonly used methods include manual dip coating, mobile dip coating, centrifugal dip coating and vacuum dip coating. These methods are suitable for the painting of hardware parts, steel pipe racks, electromechanical appliances and fibers.
3. Spraying method: spray paint droplets with a spray gun and disperse them on the surface of the coated object. At present, the most commonly used methods are air spraying, thermal spraying, high-pressure airless spraying and double-nozzle spray gun spraying.
① Air spraying method: the paint is sprayed from the nozzle of the spray gun, and the compressed air generated by the air compressor generates negative pressure at the nozzle, which makes the paint flow disperse into particles and shoot at the surface of the coated object. The injection pressure of the air compressor is 2-4 kg/cm2, and the distance between the muzzle and the coated object is 20-40 cm. The construction proficiency of the operator determines the quality of painting. ② Thermal spraying method: preheat the coating to 40-60℃ before construction, and preheat it with compressed air with the pressure of 1.7-2kg /cm2. This method saves control and pollution, and can also increase the thickness of the coating. The air spraying method used in heavy anti-corrosion engineering has good quality. (3) The high-pressure airless spraying method is to drive a high-pressure pump to pressurize the paint 100-200 kg /cm2. It is sprayed through a special nozzle (0.2- 1mm) and atomized into a very fine streamline in the atmosphere. Streamlines become very fine particles and are deposited on the surface of the workpiece due to strong surface force. This coating method greatly reduces the paint mist flying and has high production efficiency. Especially when air spraying is not used, the moisture in the air is compressed, which significantly improves the quality of fluorocarbon paint and other coatings. And that thickness of the coat film can be thin or thick. (4) Two-port spray gun method, which is designed for two-component fluorocarbon paint, polyurethane paint and polyester paint, is mainly used in construction occasions where a large number of paints are used in a large number of operations. Reduce the possible condensation in the use of coatings and the waste of coating preparation. In particular to a waterborne two-component polyurethane coating. The curing agent is contacted with a multi-component polymer in a short time, mixed and sprayed on the surface of an object in the laminar flow at the muzzle. After the water evaporates, the A and B components are crosslinked to form a cured paint film.
4. Roller coating method: Dip the dry roller in paint and roll it on the surface of the coated object, and transfer and deposit the paint on the surface of the coated object under pressure. The internal and external walls of buildings are generally painted by hand, and the pre-coating of steel plates and aluminum plates is painted by mechanical roller and color steel. That is, the metal is rolled into a continuous thin plate with a certain width, and the coating is applied randomly on line, and then cured for industrial and architectural applications. 5. Flow coating method: large-area plane coating, such as aluminum-plastic hanging board, is carried out by using a spray paint machine. Construction viscosity is 30-50 seconds, saving solvent, smooth coating, no dust flying and high quality. This method can also be used for wet-to-wet coating construction.
Third, the construction procedure of paint a) The purpose of primer construction is to achieve a good combination between metal and subsequent paint coatings and form a solid covering layer. In order to effectively prevent metal corrosion and prolong the service life of the coating, it is of great significance to correctly select the coating process of primer. Primers are divided into: maintenance primer, sealing primer and general primer. (1) curing primer, with quick drying, welding or gas cutting steel processing without toxicity and quality impact, strong adhesion and suitable weather resistance as the main requirements. Common maintenance primers include phosphating primer, zinc-rich primer and aluminum powder primer. Zinc-rich primer is mainly used for coating steel workpieces. The zinc powder content can reach 90-80%, and it can be protected for a long time under harsh corrosive conditions. Phosphating primer has high corrosion resistance, resistant to steel, aluminum, zinc, steel, tin and water metal materials. Primer with good adhesion to ceramic tile. (2) Seal primer, which generally seals the surface of water, turpentine and fatty acid in wood to prevent it from penetrating into the coating surface. The concrete surface of some old buildings. Due to long-term use, oil seeps into the pores on the surface of ceramic tiles, which will lead to foaming, peeling or discoloration of the paint film. Therefore, after surface treatment, the sealing primer should be applied, and then other paints should be applied. (3) Functional primer, such as waterproof penetration, plastic pipes and special workshops need anti-static, so as to avoid the charge accumulation caused by the working medium in motion and cause safety accidents. , all need to use functional primer. For example, when choosing anti-static primer, it is also required to choose conductive paint with anti-static function. There are conductive epoxy paint, conductive polyurethane paint and inorganic zinc silicate heavy-duty anticorrosive primer on the market. Combined with special needs, we also developed conductive paint primer and topcoat containing fluorine resin for selection. ④ Universal primer can not only improve the adhesion of paint layer, but also reduce the coating cost. It can also be divided into primary primer, secondary primer and antirust primer. The first primer has more pigments and less resin base. Emphasis is placed on enhancing adhesion to the coating surface and providing appropriate elasticity. Directly coated on the surface of the object, dried after coating, and then coated with a second primer after polishing.
B) Putty construction: Putty is thick slurry with large consistency. Except for a small amount of binder, most of them are pigments and body pigments, which have great consistency. Generally, a scraper or scraper is used to scrape on the paint film of the first primer to fill up the small defects, pits and scratches left after polishing, so as to form a smooth surface for one coating. Putty scraping is an essential process in special decorative coatings. The putty layer is easy to shrink and has poor elasticity. In case of air temperature, air temperature change or painting before the putty layer is wet, it is easy to make the coating crack, fall off and blister. Putty must not be scraped too thick, generally below 0.5 mm, otherwise it is not easy to dry out and easy to shrink and crack. If you need to fill in those irregularities, you can scrape them several times. You need to wait until the front is dry before scraping the putty in the back. Generally, epoxy putty is mostly used for advanced coating construction, or special putty is used for fluorine coating construction. Because epoxy putty has good adhesion, fast drying, good strength after drying and water and acid resistance. If the putty is thick and thick, thinner can be used to adjust the thickness, but the putty should not be used too much. Putty is used for building external walls, because it is necessary to prepare putty to fill the cracks in the wall and cement pores in order to smooth out a large area of unevenness. Emulsified epoxy resin or styrene-acrylic emulsion can be used as rubber compound, a certain amount of zinc sulfate and zinc oxide solution can be added, and white cement and white powder 1: 1 can be added to make putty. Flat and smooth parts of a large area. Cracks and air holes are allowed in the cement calendered wall surface scraped flat with a scraper. Before the putty hardens, smooth it with a trowel and polish it with sandpaper after drying. Some exterior walls use alkali-resistant primer and putty. It is not easy to use 107 glue as putty glue. If the wall is uneven, you can wipe it several times. Ensure that the wall surface is flat at every separation surface, so that the finished product surface is smooth and beautiful. Fiberboard and materials must also be putty. In addition to filling the board surface, putty should be made thinner and flatter, so that the putty can fill the gaps and pores, and the coating can be smooth.
Evenly spread on the surface of the material. In order to ensure the engineering quality, especially fluorocarbon paint.
C) Construction of topcoat: Generally speaking, topcoat should be coated on primer and putty and polished. The topcoat here refers to fluorocarbon paints of various colors, sometimes including fluororesin varnish covering the colored paints. Top coat is mainly applied by brushing or spraying. Roller coating is very uniform in the construction inside and outside the building. Generally speaking, the following points should be paid attention to in construction: ① Stir carefully after hearing it, and add special thinner for fluorocarbon paint to adjust when it is too thick. Do not dilute fluorocarbon paint with solvents at random. Diluent can be xylene: butyl acetate = 1: 1-2, preferably polyurethane. The viscosity of fluorocarbon paint should be controlled between 10-20 seconds, and the viscosity can be higher when it is coated with 4 cups. (2) The top coat should not be brushed once, but after brushing once, it must be dried and then brushed for the second time. The interval of each paint is more than 15 hour and less than 7 days. (3) The thickness of paint film must meet the construction requirements, and the consistency and coating area of paint mixing should be considered. Fluorocarbon paint is generally 120- 150g/ m2 (refers to the final diluted paint with viscosity of 40-70 seconds, and the diluent can be adjusted according to component A and component B), and the film thickness is 20-30 microns. ④ Try not to construct in dusty open air; Or spray in the open air with strong winds. Not suitable for rainy day construction or the temperature is too low, such as below zero. ⑤ For the construction of internal and external walls of the same object or building, all color paints should be mixed evenly before construction. ⑥ Because the edges, rivets, welds and bolts of objects lack adhesion or it is difficult to form an effective coating, these parts are particularly prone to corrosion. It is important that putty should be completely covered except putty. In order to avoid quality problems in these weak parts, paint should be painted between this part and the surface layer. Four, several main substrate surface fluorocarbon coating construction table:
Summary of coating specification table: construction table of fluorine coating on concrete base 1 name of process coating; specific gravity of coating system is more than dilution rate of coating method; weight% coating amount g/m2/ available time of driveway; (h) coating interval coating surface treatment The coated surface concrete can be completely removed from the surface only when the pH is PH= 10/0 and the water content is lower than 8%. Clean the surface after treatment, back cover, alkali-resistant primer, whitewash, spray, roll coat 10-50 15 hours or more, scrape putty within 15 days, scrape white paint within 15 hours, repair holes, cracks and concave surfaces, and polish putty within 7 days. Use 80- 180 mesh sandpaper to polish the putty, level it, and use various colors of liquid A 100 as primer. 8+00-50120 10/5 hours or more, apply a layer of fluorocarbon paint to the surface within 7 days, brush various solutions A 100B10, and spray and roll coating1208. Brush air spray roller coating10-50120815 hours less than 7 days Example: Epoxy primer can be one-component or two-component, and the proportion is according to the product description. The uneven surface can be smoothed with alkali-resistant resin and white cement.
Summary of coating specifications: construction of fluorine coating on steel surface (new surface) Table 2 Process coating name Coating system color mixing specific gravity Proportion coating method dilution proportion weight% coating amount g/m2/ channel film thickness Available time (h) Coating interval coating surface treatment Coating surface treatment adopts sandblasting or pickling to remove oil, dust and rust as much as possible. The acid should be neutralized, washed and primed once. Epoxy primer shall be painted once with liquid A 100B 20 of various colors, brushed, sprayed and rolled for 0- 16040 1024 hours or more, and painted once with gray liquid A 100B 20, brushed, sprayed and rolled for 0. Brush fluorocarbon paint once, 100B liquid 10, brush, spray and roll for more than 0-10120 ~15030824 hours, brush fluorocarbon paint once within 7 days, brush and spray. The mixing ratio of the two components is as specified. If high-grade smooth surface is required, high-grade series fluorine coatings can be used instead of air spraying.
Summary of coating specification table: construction of fluorine coating on steel surface (old surface) Table 3 Working procedure coating name coating system color matching proportion coating method dilution proportion weight% coating amount g/m2/ film thickness Available time (h) coating interval coating surface treatment Use tools such as manual grinding wheel and scraper to completely remove the rust removing layer. After removing the old paint film, use sandpaper and iron brush to completely wipe off the dirt, stickies and other attachments attached to it and dry it.
Zinc-rich epoxy resin and putty are used to repair paint-filled dents. Dry and shave once. For more than 25,024 hours, and within 15 days, coat epoxy zinc-rich ash on the bottom. Brush, spray and roll according to the instructions. Brush rolling for 0-15250-300801024 hours15 days. Brush and roll with various colors of fluorocarbon paint, liquid A 100B, liquid 10. Within 7 days after 025824 hours, the fluorocarbon paint shall be painted twice, and the liquid A 100B 10 shall be used for brushing, spraying and roller coating 0-10/20-150258 cases: Old surface treatment is particularly important. If you can sandblast, sandblast as much as possible. If sandblasting is not possible, the surface scale should be removed and used. The place where the putty is filled should be polished well. Special requirements can be made for heavy corrosion protection, and anti-corrosion pigments and fillers can be used.
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