The types and characteristics of commonly used anti-corrosion coatings are detailed

Anti-corrosion coating is a kind of coating which is widely used in modern industry, transportation, energy, marine engineering and other departments. According to the corrosion resistance and use requirements of the coating film layer, it is usually divided into conventional and heavy anti-corrosion types. China's annual losses due only to corrosion of metal materials as high as 500 billion yuan, accounting for about 5% of the gross national product
China
. Anti-corrosion coatings occupy an increasingly important position in the coatings industry, ranking second only to architectural coatings in size. Therefore, anti-corrosion coatings are of great significance to the development of our country.China's anti-corrosion coatings are mainly used in the chemical and petroleum industry, railways, roads and bridges, metallurgical industry, power and energy industry, machinery and textile industry, industrial products, automotive, marine and container industry. Among them, the largest industries are the chemical and petroleum industries, which include oil field facilities, pipelines, offshore platforms, petrochemical plant steel structures and reinforced concrete structure corrosion protection, at the same time, the construction and maintenance of railways and road bridges are also anti-corrosion coating applications, in addition, industrial products and marine anti-corrosion areas such as automobiles, ships are also the largest demand point of the anti-corrosion coatings market.China's national defense rotting paint market, along with China's infrastructure construction, industrial restructuring and the development of emerging industries, anti-corrosion coatings have undoubtedly become an important field and branch of the paint industry and market system, heavy anti-corrosion coatings after decades of development in China has formed the Bohai Bay region, the Pearl River Delta, the Yangtze River Delta three regional patterns., the main types of anti-corrosion coatings 1, grease coatings
grease coatings are dry oil as the main film coating. It is characterized by easy production, good brushing, good wetting, low price, paint film flexibility, but paint film drying slow, soft film, poor mechanical performance, acid and alkaline resistance, water resistance and poor resistance to organic solvents. Dry oil is often combined with anti-rust pigments to form anti-rust paint, used in the corrosion-resistant environment is not high.2, raw paint
also known as national paint, large paint, is one of China's special products. Raw paint is a milky, sticky liquid that is cut from the bark of a growing lacquer tree and filtered out by a fine cloth to remove impurities. After it is applied to the surface of the object, the color quickly changes from white to red, from red to purple, and over a longer period of time can be turned into a hard and shiny black paint film. Paint phenol is the main component of raw paint, the content of 30% to 70%. Generally speaking, the higher the content of paint phenol, the better the quality of raw paint. Raw paint adhesion is strong, paint film tough, good gloss, it is resistant to soil corrosion, more resistant to water, oil. The disadvantage is that it is toxic and irritable to people's skin. In addition, it is resistant to strong oxidants and poor alkaline. Now there are many modified raw paint coatings, to varying degrees to overcome the above shortcomings.3, phenolic resin
mainly alcohol-soluble phenolic resin, modified phenolic resin, pure phenolic resin and so on. Alcohol-soluble phenolic resin coating corrosion resistance is good, but the construction inconvenience, flexibility, adhesion is not very good, the application is limited. Therefore, it is often necessary to change the phenolic resin. Such as pine modified phenolic resin and oil refining, add a variety of pigments, by grinding can be made a variety of magnetic paint, its paint film tough, low price, widely used in furniture, doors and windows coating. Pure phenolic resin coating adhesion, water resistance to wet heat, corrosion resistance, good weather resistance.4, epoxy coating
epoxy coating adhesion is good, metal, concrete, wood, glass, etc. have excellent adhesion; However, the resistance to aging is poor. Epoxy anti-corrosion coatings are usually composed of two components, epoxy resin and curing agent. The properties of the curing agent also affect the performance of the paint film. Common curing agents are:(1) lipamine and its modifiers. Characterized by temperature-at-temperature curing, unalmed fatty amines are more toxic.
(2) aromatic amines and their modifiers. Characterized by slow reaction, often need to heat curing, toxicity is weak.
(3) polyamide resin. It is characterized by better weather resistance, less toxicity, good elasticity and slightly poor corrosion resistance.
(4) phenolic resin, formaldehyde resin and other synthetic resins. These resins and epoxy resins are interlinked into a film after being baked at high temperatures, and the paint film has outstanding corrosion resistance and good mechanical properties and decorative properties.
epoxy resin is one of the most commonly used thermo-solid resins, widely used in advanced composite resin substations, high-temperature adhesives, electronic end-end materials, high-temperature insulation coatings and other high-tech fields, due to epoxy resin added curing agent curing cross-link density, there is a large internal stress, brittleness, impact resistance and poor humidity and heat resistance and other shortcomings.epoxy resin coating is a single-part coating system with epoxy ester resin as a film. Epoxy ester resin is a combination of epoxy resin and vegetable oil fatty acid esterification. Compared with the general epoxy coating, the coating is less expensive and less alkaline. Commonly used as a variety of metal primers and chemical plant outdoor equipment corrosion-resistant paint.5, polyurethane coatings
polyurethane resins used in corrosion-resistant coatings often contain two components: isocyanate-based - NCO and hydroxyl. When used, two parts are mixed and the reaction cures to produce polyurethane (polyurethane). Polyurethane coating features:
(1) good physical and mechanical performance. Paint film hard, flexible, bright, plump, wear-resistant, strong adhesion.
(2) excellent corrosion resistance. Oil, acid, chemical and industrial exhaust. It is slightly less alkaline than epoxy coatings.
(3) aging resistance is better than epoxy coatings. It is commonly used as a paint and can also be used as a primer.
(4) polyurethane resin can be mixed with a variety of resins, can be adjusted over a wide range of formulations to meet a variety of use requirements.
(5) can be cured at room temperature or heated, and at lower temperatures (0 degrees C) can also be cured.
(6) polycyanate parts of the storage stability is poor, must be isolated moisture, so as to avoid freezing. Polyurethane coatings are expensive but have a long service life.
6, vinyl coating
ethylene resin corrosion-resistant coating mainly refers to vinyl chloride, ethylene acetate, ethylene, propylene and other single-system resin as a film coating. One of the perchloroethylene coatings has been a large number of production and applications. Perchloroethylene coating can form a dense paint film, chemical corrosion resistance is good, but the stability of light and heat is poor, long-term use should not exceed 60 degrees C, the metal adhesion is poor. The coating is rich in raw materials and has been widely used to prevent chemical atmospheric corrosion.7, furan resin coating
furan resin coating resistant to a variety of non-oxidizing inorganic acids, electrolyte solutions, a variety of organic solvents, alkaline resistance is also outstanding, but antioxidant is not good. Furan resin series anti-corrosion coatings include sterol resin coatings, acetaldehyde formaldehyde resin coatings and modified furan resin coatings.8, rubber coatings
rubber anti-corrosion coatings to chemical treatment or mechanical processing of natural rubber or synthetic rubber as film-forming substances, plus solvents, fillers, pigments, catalysts and other processing.
(1) chlorinated rubber coatings. The coating has good water resistance, salt water and salt spray resistance, certain acid and alkali corrosion resistance, less than 50 degrees C can withstand 10% HCl, H2SO4, HNO3, different concentrations of NaOH and wet Cl2. But not solvent resistant, aging resistance and poor heat resistance. The coating is widely used in ships, harbors, chemicals and other occasions.(2) neoprene coating. The coating is ozone-resistant, chemical-resistant, alkaline and weather-resistant, oil- and heat-resistant, and can be made into a peelable coating. The disadvantage is poor storage stability, the coating is color-changing, not easy to make white or light paint.(3) chlorine-sulfonated polyethylene rubber coating. Produced by a polyethylene resin reacting with chlorine gas and sulfur dioxide (or chlorine sulfonate). The coating has excellent anti-ozone properties, significant weather resistance, low water absorption, oil resistance and temperature resistance, and can be used above 120 degrees C, and not brittle at -50 degrees C.9, asphalt coatings
asphalt is one of the most important anti-corrosion coatings. Especially coal coking asphalt as the best, coal coking asphalt coating is cheap, has the following advantages:
(1) water resistance, immersion in water for 10 years its water absorption rate is only 0.1%
to 0.2%; 2) resistance to the erosion of some chemical media,
(3) on the under-rusted steel surface is still good wetting,
(4) solid content is high, thick film,
(5) low price.
its disadvantage is the cold winter hair brittle, summer and summer hair soft, after exposure to some ingredients volatile escape will make the paint film crack. These disadvantages can be improved by adding some other resins. For example, the addition of chlorinated rubber can improve the dryness of asphalt coatings, improve the shortcomings of winter crisp summer soft, add epoxy resin-made epoxy asphalt coatings, can be both asphalt coatings and epoxy coatings advantages, in the anti-corrosion to obtain very satisfactory results. Asphalt paint has been used in container bottom, bottom, dock gate, fence and other occasions, anti-corrosion effect is very good.10, heavy anti-corrosion
and heavy anti-corrosion coatings are relative to the general anti-corrosion coatings. It refers to the anti-corrosion coating with anti-corrosion effect several times higher than the general corrosion coating under severe corrosion conditions. It is characterized by excellent performance of corrosion-resistant media, outstanding durability, service life of more than several years. Mainly used in marine structures and chemical equipment, storage tanks and pipelines.currently commonly used heavy anti-corrosion coatings are:
(1) as a primer of heavy anti-corrosion zinc-rich coatings. Sub-thick film organic zinc-rich coatings, zinc-rich pre-coated primers and inorganic zinc-rich coatings three series.
(2) heavy corrosion-resistant intermediate coatings and finishes. This type of coating can be directly applied to zinc-rich primers, mainly chlorinated rubber system, ethylene resin system, epoxy system, polyurethane system, chlorine sulfonated polyethylene system, epoxy tar system and other heavy corrosion-resistant coatings. (3) glass phosphorus sheet heavy corrosion-resistant coating.
(4) epoxy mortar heavy corrosion-resistant coating.
(5) fluorine-containing coatings. Such as Teflon vinyl chloride coatings, fluoroelas rubber coatings.
addition, a new type of nano-coating has appeared in the market, the anti-corrosion effect is better. A new acid-base-resistant coating material consisting of nano-alumina, nano-zirconia, nano-titanium oxide and nano-silicon oxide. This type of anti-corrosion coating has excellent high temperature resistance, strong acid resistance (hydrochloric acid, sulfuric acid, nitric acid, organic acid, etc.), strong alkali resistance (sodium hydroxide, potassium hydroxide, etc.), strong corrosion resistance, high salt resistance, oil immersion, wear resistance, pressure resistance, impact resistance, and other advantages. Ideal for applications where strong acids, alkalis and corrosives are required. nano-base material has a strong isolation effect, with dense characteristics, so that light and various corrosive molecules can not penetrate the coating, extreme corrosion resistance. The nanoparticles themselves have a high hardness, which improves the wear resistance of the nanocoat. And can quickly and easily repair the coating for various reasons of damage, greatly extend the service life of the equipment. However, excellent nanocoated coatings require uniform dispersion of nanoparticles and changes to the surface of nanoparticles to improve surface adsorption between particles. These two points are the difficulties of nano-coatings. II, the role of anti-corrosion coatings (1) shielding action: the basic condition of electrochemical corrosion of steel surface is that the steel surface must have water, oxygen, ions and the presence of ions, electron circulation (conductive). The shielding of anti-corrosion coating layers prevents water, oxygen and ions from reaching the steel surface through the coating. Second, the coating also blocks the direct chemical corrosion of acid and alkalis and the industrial atmosphere. (2) corrosion-retarding effect: in the anti-corrosion coating layer (especially in the primer) contains chemical anti-rust pigments, when there is water, can be removed from these rust-proof pigments corrosion-retarding ions, these ions can also make the corrosion cell of an electrode polarization (or passivation) to inhibit corrosion. Therefore, the corrosion-reprieve effect can make up for the lack of shielding. In turn, the shielding effect can prevent the loss of corrosion ions, so that the corrosion inhibition effect is stable and long-lasting. (3) Cathodic protection: If there are more active metal (metals with lower electrode potence) powders than steel in the coating, such as zinc powder or aluminum powder, they can form a sacrificing anode to steel, as long as these active metal powder content between the metal powder particles and between the metal powder and the steel substrate to a point of contact, can protect the steel from corrosion. years, anti-corrosion coatings and have made great progress, and object protection in harsh environments has played an important role. It can be said that the level of development of heavy anti-corrosion coatings marks the level of development of a country's anti-corrosion coatings and even marks a country's level of scientific and technological development. 3. The choice and construction of anti-corrosion coatings 1, the choice of coating varieties
a wide variety of anti-corrosion coatings, their properties and uses vary, the correct selection of the coating corrosion-proof effect and service life is very important. When selecting should be considered:
(1) the surface material properties of the coated object. Such as ferrous metal can choose iron red, red Dan primer, and red Dan primer on aluminum and other non-ferrous metals not only do not have a protective effect, but will play a destructive role.
(2) the environment in which the object is painted is used. Anti-corrosion coatings are very targeted to the environment, according to the specific use of the environment, such as the type of media, concentration, temperature, equipment operation and other factors to choose the most suitable paint varieties.
3) construction conditions. Suitable coating varieties should be selected according to the actual conditions of the construction site. For example, in poor ventilation conditions on-site construction should be using solvent-free or high solid or water-based corrosion-resistant coatings. Self-drying coatings can only be used in sites that do not have baking and drying. (4) technology, economic comprehensive effect. Consider not only whether the technical performance is excellent, but also the economic rationality. In economic accounting, material costs, surface treatment costs, construction costs, coating performance and service life, maintenance costs and other comprehensive considerations. 2, anti-corrosion coating construction principles
the quality of coating construction has a great impact on the performance of the coating. In the actual coating process due to improper construction methods and can not achieve the expected anti-corrosion effect of many examples. In particular, many high-performance corrosion-resistant coatings are extremely sensitive to construction methods, and only in strict accordance with their respective construction conditions can the construction form a normal coating, to achieve the expected anti-corrosion protection. (1) substrate must be subject to strict surface treatment. Steel substrates must be rust-free and oil-free, and phosphate treatment can be specific.
(2) to ensure the necessary coating thickness. The thickness of the corrosion-resistant coating must exceed its critical thickness in order to be protective, typically 150 m-200 m.
(3) control the temperature and humidity of the coating site