Anticorrosive material is a kind of material which can inhibit the occurrence of chemical and electrochemical corrosion of the anticorrosive object. The commonly used anticorrosive materials in the installation project mainly include a variety of organic and inorganic coatings, glass fiber reinforced plastics, rubber products, inorganic plates, etc.
classification
Coatings can be divided into two categories: oil - based paint (film - forming material for dry oil) and resin - based paint (film - forming material for synthetic resin). It is coated on the surface of the object by a certain coating method, the formation of a thin coating after curing, so as to protect the surface of equipment, pipes and metal structures from chemical atmosphere and acid, alkali and other media corrosion.
Antirust paint and primer coating according to its role, can be divided into primer and topcoat two. Their distinction is the pigment of primer is more, can burnish, lacquer emphasizes to the adhesion force of the thing face, and its lacquer film of anticorrosive paint is in satisfying the requirement of the performance such as water resistance, alkali resistance.
1) raw lacquer (also known as lacquer). Taupe viscous liquid, with acid resistance, solvent resistance, water resistance, oil resistance, wear resistance and strong adhesion and other advantages, the disadvantage is not resistant to strong alkali and strong oxidant, toxic. The operating temperature is 150℃.
2) urushiol resin paint. Is the raw paint dehydration condensation polycondensation with organic solvent dilution, changed the paint toxicity, slow drying, construction inconvenience and other shortcomings, but it is not resistant to the sun ultraviolet irradiation, at the same time can not be long.
3) phenolic resin paint. With good electrical insulation and oil resistance, able to withstand 60% sulfuric acid, hydrochloric acid, a certain concentration of acetic acid and phosphoric acid, most salts and organic solvents and other media corrosion, but not strong oxidants and alkali.
4) epoxy-phenolic paint. It is prepared from epoxy resin and phenolic resin soluble in organic solvents (such as xylene, butyl acetate, cyclohexanone, etc.). It has good mechanical properties, alkali resistance, acid resistance, solubility and electrical insulation.
5) epoxy resin coating. Has good corrosion resistance, especially alkali resistance, and has a good wear resistance, paint film has good elasticity and hardness, shrinkage rate is low, the service temperature is generally 90~100℃.
6) vinyl perchloride paint. It has good resistance to industrial atmosphere, seawater, acid, oil, salt spray, mildew and combustion, but it is not resistant to the corrosion of phenols, ketones, lipids, benzene and other organic solvent media. The maximum operating temperature is about 70℃, in addition to its weak adhesion to the metal surface.
7) asphalt paint. Low price and more, at room temperature can withstand nitrogen oxide, sulfur dioxide, sulfur trioxide, ammonia, acid fog, chlorine, low concentration of inorganic salt and concentration of less than 40% of alkali, seawater, soil, salt solution and acid gas and other media corrosion. However, it is not resistant to organic solvents such as oils, alcohols, lipids, hydrocarbons, strong oxidants and other media such as corrosion, and the stability of the sun is poor, heat resistance in 60℃.
8) furan resin paint. It has excellent resistance to acid, alkali and temperature. Disadvantage is the existence of brittle, and metal adhesion is poor, dry will contract.
9) polyurethane paint. The highest heat resistance is 155℃, with good resistance to chemical corrosion, oil, wear and adhesion, paint film toughness and electrical insulation are good.
10) inorganic zinc rich paint. Simple construction, cheap price, with good water resistance, oil resistance, solvent resistance and resistance to alternating wet and dry salt fog, suitable for seawater, clean water, ocean atmosphere, industrial atmosphere and oil and other media. The heat resistance is about 160℃.
11) new paint
Polyurethane paint. Construction is convenient, non-toxic, low cost, and resistant to acid, salt, all kinds of diluent.
(2) epoxy coal asphalt. It is mainly composed of epoxy resin, coal asphalt, filler and curing agent. It combines the advantages of high mechanical strength, high adhesion, resistance to chemical medium and corrosion resistance of coal pitch. The coating temperature is between -40~150℃. There is no change in acid, alkali, salt, water, gasoline, kerosene, diesel and other general diluent soaking for a long time.
3 polyethylene anti-corrosion paint. It has good mechanical strength, electrical property, anti-ultraviolet, anti-aging and anti-anode stripping properties, and its anticorrosive life can reach more than 20 years.
structure
Although the variety of coating is very much, but in terms of its composition, basically can be divided into three parts: main film material, secondary film material and auxiliary film material.
1. Main film-forming materials
(1) fuel. Oils are natural products that come from plant seeds and animal fats. The dry curing reaction of oil is mainly oxygen in air and oil
Anti-corrosion materials
Anti-corrosion materials
The unsaturated double bond in. All aspects of the performance of natural oil, especially corrosion resistance, aging resistance performance than many synthetic resin, it is rarely used for corrosion protection coating alone, but it can be with some metal oxides or metal saponification together with the metal rust action, so the oil can be used to modify a variety of synthetic resin to make matching rust protection primer.
(2) natural resins and synthetic resins. Natural resin refers to asphalt, lacquer, natural rubber, etc. Synthetic resin is to point to epoxy resin, phenolic resin, furan resin, polyester resin, polyurethane resin and ethylene resin, perchloroethylene resin and fluorinated resin, they are commonly used in the corrosion resistant coatings in the main film material.
2. Secondary film-forming materials (pigments)
Paint coating is one of the main ingredients, add pigment in paint make coating not only ornamental, more important is can improve the physical and chemical properties of coatings, improve the mechanical strength of the coating, such as adhesion, penetration resistance and corrosion resistance ability, and filter the harmful light, thereby enhancing the weatherability and protective coating. It is mainly divided into anti-rust pigments, constitution pigments and coloring pigments:
Anti-rust paint. According to different antirust mechanism can be differentiated to learn antirust pigments, such as red lead, zinc chrome yellow, zinc powder, zinc phosphate and organic chromate, etc., this kind of pigments in the coating is by the help of chemical or electrochemical action of antirust; The other is the physical antirust pigment, such as aluminum powder, mica iron oxide, zinc oxide and graphite powder, its main function is to improve the density of paint film, reduce the permeability of paint film, prevent the penetration of sunlight and water, in order to enhance the coating antirust effect.
Constitution pigment. Constitution pigment can improve the weatherability, impermeability, abrasion resistance and physical and mechanical strength of the coating, commonly used talc powder, calcium carbonate, barium sulfate, mica powder and diatomite.
Coloring pigments. Coloring pigment plays a major role in coloring and covering film surface in coatings.
3. Auxiliary film-forming materials
(1) solvent. It mainly plays the role of dissolving film-forming material, adjusting coating viscosity, controlling coating drying speed and so on. Some characteristics of the solvent on the coating, such as brush resistance, leveling, film rate, flow, drying, gelation, infiltration and low temperature use will have an impact.
Other auxiliary materials.
Plasticizer: used to improve the flexibility of the film, impact resistance and overcome the shortcomings of hard film brittleness, easy to crack.
Thixotropic agent: the paint in the process of brush coating has a lower viscosity, in order to facilitate the construction.
Drier: to accelerate the drying of paint film.
Surfactant, anti - mildew agent, ultraviolet absorbent and anti - fouling agent.
The type of paint is divided into three parts: the first part is the film material; The second part is the basic name, represented by two digits; The third part is the serial number. Example: H 50-2: epoxy acid resistant paint.
application
Metal material
one Glass fiber reinforced plastic
Because of the reinforcing effect of glass fiber, FRP generally has high mechanical strength and integrity, and is not easy to be damaged by mechanical impact.
There are many kinds of glass reinforced plastics, are named after the blending of synthetic resin, commonly used epoxy glass reinforced plastics, polyester glass reinforced plastics, epoxy phenolic glass reinforced plastics, epoxy coal tar glass reinforced plastics, epoxy furan glass reinforced plastics and phenolic furan glass reinforced plastics.
The general FRP lining layer consists of four parts
1. The bottom layer is the coating coated on the surface of the equipment after treatment in order to prevent rust.
2. The putty layer is mainly used to fill the uneven surface of the substrate. By leveling the putty, the paving ability of fiber products can be improved.
3, the strengthening layer mainly plays a strengthening role, so that the lining layer constitutes a whole.
4, as long as the surface is high resin layer. As it is in direct contact with the corrosive medium, it requires good compactness and impermeability.
Rubber products
Antiseptic rubber mainly refers to natural rubber. The service temperature of rubber is related to its service life. If the temperature is too high, it will accelerate the aging of rubber, destroy the binding force between rubber and metal structure, and cause the rubber to fall off. Rubber loses its elasticity at too low a temperature.
The rubber used as chemical lining is made of raw rubber after vulcanization treatment. The vulcanized rubber has certain heat resistance, mechanical strength and corrosion resistance.
There are many kinds of synthetic rubber, and polyisobutylene rubber is mainly used for chemical corrosion protection.
The highest temperature of polyisobutene rubber is generally 50~60℃. It still has good elasticity and sufficient strength at low temperature. At 50℃, the polyisobutene plate begins to soften, so it cannot withstand mechanical action. It can withstand all kinds of concentration of hydrochloric acid, less than 80% of sulfuric acid, dilute nitric acid, less than 40% of hydrofluoric acid, alkali solution and a variety of salt solution medium such as corrosion, not resistant to lead, fluorine, chlorine, bromine and some organic solvents, such as benzene, carbon tetrachloride, carbon disulfide, gasoline, mineral oil and vegetable oil and other media corrosion.
Corrosion resistant nonmetallic material
1, various brick, board and pipe lining characteristics
1) diabase plate and pipe lining is made of molten diabase. The main ingredient is silica, a gray-black material with a dense texture.
The advantage is good acid and alkali resistance, except hydrofluoric acid, above 300℃ phosphoric acid and molten alkali, to all organic acid, inorganic acid, alkali are corrosion resistant and wear resistance.
Shortcoming is brittleness is big, do not bear the impact of the weight, temperature difference is short, the plate is difficult to cut processing.
2) acid-proof ceramic tiles, boards and pipe linings are made of fire-resistant clay, feldspar and quartz by dry molding method, the main component is silica.
The advantage is good acid resistance, except hydrofluoric acid, phosphoric acid above 300℃ and strong base, corrosion resistance to all acids; Compact structure, smooth and flat surface.
The disadvantages are brittleness, poor toughness and poor temperature difference.
3) impervious graphite sheets and tube linings are made of synthetic graphite-impregnated phenolic or furan resins.
The advantages are good thermal conductivity, good temperature change, easy to machine.
The disadvantage is low mechanical strength, expensive.
2. Adhesives
1) phenolic cement. It is made of phenolic resin as adhesive, with acid as curing agent, adding acid proof filler, mixing in a certain proportion.
2) water glass cement. Also known as silica paste, by water glass as binder, sodium fluorosilicate as curing agent and acid proof filler by a certain proportion of mixing. Especially resistant to strong oxidizing acid (nitric acid, chromium acid, etc.) corrosion.
3) furan cement. It is made of furan resin as adhesive, acid as curing agent, adding acid proof filler in a certain proportion.
The development of new technologies
1. Three-layer polyolefin patch technology
If the filler is needed, the relationship between the material and the coating should be considered, which requires special filler technology, according to relevant reports
Anti-corrosion materials
Anti-corrosion materials
Stand out thousands of PIH of British company has developed a three layers of polypropylene filling mouth, a 250 m thick layer of weld first epoxy powder coating on the surface of modern pipeline, and then coated with a layer of polypropylene powder of 200 m thick, pay attention to the chemical modification of polypropylene powder is need, and then bring on 300 mm wide polypropylene composite related interface, with squeezing pliers clamping it finally.
2. Filler technology of liquid materials
On the detailed investigation using r heat shrinkable sleeve for a 370 kin long coal tar enamel anticorrosion pipeline and a lIOkra polyethylene anticorrosive pipe on the second floor, the results show that there are funnelled door rate is quite high, this paragraph 2 of anti-corruption funnelled pipe joint is as high as 80%, the serious corrosion problems of pipe are mostly because of joint failure. When using the traditional one-layer material and thermal shrinkage bushing patch technology, the most important is the cathode shielding, the qualified rate of thermal shrinkage construction is only 50%, which is the data from a large number of investigation data, the credibility is quite high. The best way to avoid this kind of problem is to make up the liquid material, which is a new technology in foreign countries.
3. Welding joint technology
Good sealing performance, good mechanical strength, wear resistance is several characteristics of the fusion joint technology, it has the characteristics of strong adaptability. It can also be used in directional drilling and desert environments where soil stress is high, and a new method has been developed abroad. For two or three layers of polyethylene coating, this technique is to attach the jacket layer to the surface of the tube and heat the jacket layer with a heating element to make the coating jacket and the jacket on the tube body dissolve.
Polyurea anticorrosive material
advantage
Spraying polyurea technology is one of the most advanced anticorrosive technologies in the world. Its technical advantages are mainly manifested in the following aspects:
(1) fast curing, can be sprayed on any surface without flowing phenomenon, 10s gel, 10min can achieve walking strength.
(2) it is not sensitive to temperature and humidity, and is not affected by environmental temperature and humidity during construction. Polyurea can be used in the low temperature environment of -28℃, but also in the wet and rainy environment.
(3)100% solid content, in line with the requirements of environmental protection, no odor in the construction and use process, especially suitable for the anti-corrosion construction of storage tank and pipe wall with poor ventilation.
(4) a single construction can meet the thickness requirements, overcome the traditional anticorrosive coating must be applied many times.
(5) polyurea coating is dense and seamless, which can withstand long-term corrosion of water, seawater, acid, alkali, salt, oil and other media, and has outstanding resistance to chemical media and soil erosion.
(6) high mechanical strength, good elongation, good impact resistance, not easy to damage under the impact of temperature and external force.
(7) good adhesion, more than 10MPa on sandblasted to Sa2.5 steel, long-term use will not fall off.
(8) the breakdown voltage is up to over 20kv/mm, with good compatibility with cathodic protection.
(9) no catalyst, good uv aging resistance, long-term use in the outdoor without pulverization, no cracking.
(10) wide operating temperature, it can be used for a long time at a temperature of 50 ~ +121℃, and modified high-temperature polyurea can be used for a long time below 150 ℃.
An overview of the
The development of spraying polyurea elastomer technology has gone through three stages: polyurethane, urethane and polyurea. The component A of the above three systems is basically the same, which is the pre-polymer and semi-pre-polymer of aromatic or aliphatic group. The difference lies in the component R. The R component of sprayed polyurethane is composed of hydroxy-terminated resin and hydroxy-terminated chain extender, and contains a catalyst to improve the reactivity. The R component of the sprayed urethane can be either a hydroxy-terminated resin or an amine-terminated resin and an amine chain extender, and generally contains a catalyst for increased reactivity. However, the R component of spraying polyurea must be composed of terminal amino resin and terminal amino chain extender, and does not contain any hydroxyl components and catalysts.
The end amino compounds with high reactivity of isocyanate component, without any catalyst, instantaneous reaction at room temperature or low temperature, can be effectively overcome the polyurethane and polyurethane/urea elastomer in construction process, due to the influence of environment temperature and humidity foaming, causing a sharp drop in material performance of fatal weakness.
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