【Metal protection】
For the reasons for the corrosion of metal to take appropriate measures to prevent corrosion of metal, commonly used methods are:
For the reasons for the corrosion of metal to take appropriate measures to prevent corrosion of metal, commonly used methods are:
[Change the internal structure of the metal] For example, the manufacture of various corrosion-resistant alloys, such as ordinary steel by adding chromium, nickel and other stainless steel.
[Protective layer method] in the metal surface covered with protective layer, so that metal products and the surrounding corrosive media isolation, thereby preventing corrosion. Such as:
1. In the steel parts coated with oil, petrolatum, paint or cover enamel, plastic and other corrosion-resistant non-metallic materials.
2. With electroplating, hot plating, sputtering and other methods, in the steel surface coated with a layer of metal is not easy to be corroded, such as zinc, tin, chromium, nickel and so on. These metals are often oxidized to form a dense layer of oxide film, thereby preventing water and air corrosion of steel.
3. The chemical surface of the steel surface to generate a layer of fine and stable oxide film. Such as machine parts, guns and other steel parts on the surface to form a layer of fine black iron oxide film.
[Electrochemical protection method] The use of the original battery principle of metal protection, trying to eliminate the electrochemical corrosion caused by the original battery reaction. Electrochemical protection method is divided into two categories: anode protection and cathodic protection. The application is more cathodic protection method.
[Handling of corrosive media] Eliminate corrosive media, such as frequent cleaning of metal equipment, placing desiccants in precision instruments, and adding a small amount of corrosion inhibitors that slow down the corrosion rate in corrosive media.
Electrochemical protection
Will be protected metal as the cathode of the corrosion of the battery, so that it is not subject to corrosion, it is also called cathodic protection method. This method mainly has the following two kinds:
[Sacrificial anode protection method] This method is the active metal (such as zinc or zinc alloy) connected to the protected metal, when the occurrence of electrochemical corrosion, this active metal as a negative oxidation reaction, thus reducing or preventing being Protect the metal from corrosion. This method is often used to protect the steel in the water and the sea shell, such as water, such as the protection of steel gates, usually in the ship's shell below the water line or near the propeller on the rudder welded a number of pieces of zinc to prevent hull Corrosion.
[Protection method of applied current] Connect the protected metal and the negative terminal of the power supply, and select a conductive positive material to connect the positive pole of the power supply. After the power, the metal surface to produce negative charge (electron) accumulation, thus inhibiting the metal loss of electrons to achieve the purpose of protection. This method is mainly used to prevent corrosion of metal equipment in soil, sea water and river water. Another method of electrochemical protection is the anode protection method, that is, by applying a voltage, so that the anode in a certain range of potential passivation process. Can effectively block or prevent the metal equipment in acid, alkali, salt corrosion.
Metal before treatment
(1) metal anti-corrosion coating surface treatment:
Usually the metal surface will be attached to the dust, oil, oxide, rust layer, contaminants, salt or loose old paint film. Where the scale is more common but most easily overlooked. The scale is a layer of dense oxide that is produced when the steel is subjected to high temperature forging, which is usually more firmly attached, but is more brittle than the steel itself, and itself is a cathode that accelerates metal corrosion. If you do not clear the direct coating of these substances, is bound to affect the coating adhesion and corrosion resistance. According to statistics, about 70% of the paint problem is due to improper surface treatment caused by. Therefore, for a metal anti-corrosion coating paint system performance reflects the appropriate surface treatment is essential ...
(2) metal corrosion surface cleaning level:
That is, cleanliness, there are two representative international standards: one is the United States 85 years to develop "SSPC-"; the second is the Swedish 76 years developed "Sa-", it is divided into four levels were Sa1, Sa2 , Sa2.5, Sa3, for the international common general standards, as follows: Sa1 level - the equivalent of the United States SSPC-SP7 level. Using a simple simple manual brush, sand cloth grinding method, which is the four cleanliness of the lowest level, the protection of the coating is only slightly better than the workpiece is not used. Sa1-level technical standards: the workpiece surface should not be visible oil, grease, residual oxide, rust, and residual paint and other dirt. Sa1 level is also called manual brush to clean up level. (Or sweep level)
Sa2 - equivalent to the US SSPC-SP6 level. The use of sandblasting cleaning method, which is sandblasting the lowest level, that is, the general requirements, but for the protection of the coating than the manual brush to clean up to improve a lot. Sa2-level technical standards: the surface of the workpiece should not be visible greasy, dirt, scale, rust, paint, oxides, corrosive substances, and other foreign substances (except defects), but the defect is limited to no more than the surface per square meter 33%, may include minor shadows; a small amount due to defects, rust caused by a slight decolorization; oxide and paint defects. If the original surface of the workpiece has a dent, the slight corrosion and paint will remain at the bottom of the dent. Sa2 level is also called commodity cleaning level (or industrial grade).
Sa2.5 - is widely used in industry and can be used as acceptance technical requirements and standards level. Sa2.5 level is also called near white clean level (near white or white). Sa2.5 grade technical standards: the same as the first half of the Sa2 requirements, but the defect is limited to not more than 5% per square meter of the surface, including a slight shadow; a small amount due to defects, rust caused by a slight decolorization; The
Sa3-level is equivalent to the US SSPC-SP5 level, is the highest level of industrial processing, also known as white cleaning level (or white level). Sa3-level technical standards: the same as Sa2.5 level, but 5% of the shadows, defects, corrosion and so have to exist.
With the development of modern industry, the emergence of a number of new industrial areas and the construction of many modern projects, anti-corrosion coatings to withstand the environment capacity and service life put forward higher requirements. Commonly used anti-corrosion coatings have been unable to meet these needs. The concept of "heavy-duty coating", commonly referred to as heavy-duty coatings, is used in harsh corrosive environments, including primer and topcoat. Simply put: heavy anti-corrosion coating is longer life, can adapt to more demanding use of the environment called heavy anti-corrosion coating. In the chemical atmosphere and marine environment, heavy anti-corrosion coatings can generally be used for 10 years or more, in acid, alkali, salt and solvent medium, and in a certain temperature corrosion conditions, the general should be able to use more than 5 years.
[Anti-corrosion commonly used materials]
The application of heavy anti-corrosion coatings involves the modernization of various fields, large industrial and mining enterprises: chemical, petrochemical, steel and large mining smelting pipes, storage tanks, equipment, etc .; important energy industry: natural gas, tubing, oil tank, power transmission , Nuclear power equipment and coal mines; modern transport: bridges, ships, containers, trains and cars; emerging marine engineering. Offshore facilities, coastal and bay structures and offshore oil drilling platforms. Epoxy resin as the main film material coating known as epoxy paint. Each year about 40% of the world's epoxy resin used in the manufacture of epoxy coatings, most of which for the field of corrosion. Epoxy anti-corrosion coating is currently the world's most widely used, one of the most important heavy anti-corrosion coating.
Anticorrosion Engineering Materials:
1, high chlorinated polyethylene anti-corrosion coatings, such as MX53-4 colored chlorinated polyethylene anti-corrosion finish (indoor and outdoor), MX53-1 high chlorinated polyethylene iron red anti-rust paint, MX53-2 high chlorination poly Vinyl cloud iron anti-rust paint, MX53-3 high chlorinated polyethylene cloud iron intermediate paint
Second, chlorosulfonated polyethylene anti-corrosion coatings, such as J52-4 chlorosulfonated polyethylene cooling tower moisture-proof paint (bottom / side, two components), J52-5 chlorosulfonated polyethylene gas cabinet special anti-corrosion paint (bottom / / Side, two component), J52-6 chlorosulfonated polyethylene underground pipe coating (bottom / side, two component)
Third, the silicone high temperature anti-corrosion coatings, such as MW-600 silicone high temperature anti-corrosion coating (bottom / side, two components), MW-700 silicone high temperature anti-corrosion coating (bottom /
Four, epoxy anti-corrosion coatings, such as H06-4 epoxy zinc-rich primer (three components), H06-12 epoxy cloud iron intermediate paint (two components), HL52-3 epoxy asphalt anticorrosive paint (bottom / face , Two-component)
Five, chlorinated rubber coatings, such as J53-33 chlorinated rubber iron red anti-rust paint, J53-4 chlorinated rubber anti-corrosion finish, J53-5 chlorinated rubber thick paste
Six, polyurethane anti-corrosion coating, such as S52-3 polyurethane anti-corrosion finish (two-component), S52-30 polyurethane silver anti-corrosion paint (three components), S52-10 polyurethane modified interpenetrating network anti-corrosion coating (two-component)
Seven, fluorine resin coating, such as JF fluorine resin anti-corrosion coating (bottom / side, two-component)
8, oil tank wall paint, such as H66-1 oil anti-static coating (two components), H52-3 finished oil tank wall coating (bottom / surface, two components), HL52-10 epoxy asphalt oil paint (bottom / Surface, two-component)
Nine, empty signs, road signs paint, such as J67-1 chlorosulfonated polyethylene high altitude logo paint (two components), B56-1 acrylic modified road marking scribing paint, T56-2 hot melt road marking paint
10, inorganic zinc silicate, zinc-rich primer, such as E06-1 inorganic zinc silicate primer (two-component), E06-2 inorganic zinc-rich primer (two-component), E06-10 inorganic phosphate zinc Paint (two component)
11, food drinking water tank wall paint, such as H86-1 epoxy drying canned primer, H86-2 epoxy drying canned enamel, H86-3 epoxy high solid drinking water tank paint (bottom / side, two components)
12, floor coatings, such as H77-1 thick film industrial floor coatings (two components), H77-2 anti-static industrial floor coatings (two-component), H77-3 wear-resistant industrial floor coatings )
Thirteen, with rust primer, such as 70 with rust primer
14, fire retardant coating, such as PH-1 steel structure expansion fire retardant paint, PH-2 general-purpose fire retardant coating, PH-3 non-metallic structure fire retardant coating
15, amino resin paint, such as A01-1 amino drying varnish, A04-9 amino drying enamel, A16-50 amino hammer drying paint
16, alkyd paint, such as C06-1 alkyd iron red primer, C53-31 red dan alkyd antirust paint, C43-1 alkyd hull paint
Seventeen, phenolic resin paint, such as F03-1 phenolic blending paint, F53-33 iron red phenolic antirust paint, F04-1 quick-drying silver enamel
18, other, C-1 quick-drying anti-rust oil, JN533 iron red cyanide anti-rust paint (two-component), JN533 cloud iron cyanide condensate intermediate paint (two components), L01-13 asphalt varnish
[Rust before industrial anti-corrosion]
Introduction of anti - rust materials
1, the role of anti-rust paint
Corrosion-resistant paint for the anti-rust paint more types, which are common in the following categories:
① with the film forming agent to form a dense anti-corrosion coating;
② pigment is alkaline substances, soluble in water is the formation of alkaline environment;
③ water-soluble components to reach the surface of the metal surface passivation;
④ with the reaction of acidic substances to lose its ability to corrode;
⑤ The water-soluble component or the reaction product with the film-forming agent is dissolved in water to become an anticorrosive component.
Antirusts of anticorrosive pigments are usually present at the same time, and their corrosion mechanisms include the following physical, chemical and electrochemical aspects.
① physical anti-corrosion effect. Appropriate with the oil film with the reaction of the pigment can be a dense anti-corrosion coating to enhance the physical anti-corrosion effect. For example, lead-based pigments react with oil to form lead soap to make the anti-corrosion coating dense, thereby reducing the penetration of water and oxygen harmful substances. Phosphate pigments hydrolyze to form insoluble base acid salts, with the effect of blocking pinholes in the anti-corrosion coating. The iron oxide or with a scaly mica powder, aluminum powder, glass flakes and other pigment filler can reduce the permeability of anti-corrosion coating, play a physical anti-corrosion effect.
② chemical anti-corrosion effect. When the harmful acidic alkaline substances into the anti-corrosion coating, can play a neutral role into harmless substances, which is an effective anti-corrosion method. In particular, clever use of zinc oxide, aluminum hydroxide, barium hydroxide and other amphoteric compounds, can be easily achieved in the acidic or alkaline harmful substances and anti-corrosion effect, or with water, acid reaction to produce alkaline substances. These alkaline substances adsorbed on the surface of steel to keep the surface alkaline, in the alkaline environment, steel is not easy to rust.
③ electrochemical anti-corrosion effect. Water and oxygen from the pinhole of the coating through the anti-corrosion coating, and dispersed in the anti-corrosion coating in the anti-rust paint to form anti-corrosion ions. This kind of moisture containing anti-corrosion ions to reach the metal surface, the steel surface passivation (so that the potential rise), to prevent the dissolution of iron ions, chromate pigments have this feature. Or the use of metal electrodes lower than the metal to protect the steel, such as zinc-rich coating is due to zinc electrode potential than steel, play the role of sacrificial anode and the steel is not easy to be corroded.
2, anti-rust function of the oil
(1 Overview
Threaded fasteners are available from ordinary bolts, nuts, screws, high strength, high performance, high precision, high added value and non-standard shaped parts. Their rust-proof packaging methods are basically the same. For the surface oxidation, phosphating, black screw fasteners are mostly used surface coating, dip rust oil, plus plastic packaging.
Antirust grease is the basic components of the oil by adding one or more anti-rust additives (also known as oil-soluble corrosion inhibitor) and its auxiliary additives, it is easy to use, low cost, good effect, simple operation, the current tight The firmware industry is heavily used.
(2) research and development
Domestic anti-rust grease from the 1960s began to appear goods, by the Wuhan Institute of Materials Protection developed GB4879-1985 "rust-proof packaging" standard, lists the domestic anti-rust oil types and indicators.
Nearly two decades, the rapid development of anti-rust oil, every year a variety of new products come out, the following for a brief introduction.
2.1 thin layer of anti-rust oil
RPA type, GF type solvent-based thin-layer anti-rust oil, the majority of fastener business of a variety of different processes for production applications, proved fasteners on the product has good anti-rust performance, while easy, Bright, solvent evaporation less, the amount of province, for the thick layer of anti-rust oil one-third of the following, so save production costs more than two-thirds. HH932 dehydration rust-proof oil, can guarantee no rust within ten months; JN-2 anti-rust oil, the main purpose for the fastener at room temperature after the treatment. Thin layer of anti-rust oil can be used for indoor processes rust, can also be used for packaging storage rust.
2.2 wax film rust-proof oil
In the solvent dilution type anti-rust oil or ultra-thin layer of anti-rust oil by adding some oil-soluble wax, wax can be obtained rust-proof protective film, can significantly improve the oil film resistance to salt spray and resistance to atmospheric performance. However, the wax at room temperature is solid or semi-solid, easy to precipitate in the oil, affecting the appearance and quality of oil, and even difficult to obtain the desired anti-rust effect, therefore, looking for oil-soluble, can significantly improve the anti-rust Of the wax is to obtain good stability, film uniformity waxy anti-rust oil key.
Wax film rust-proof oil is composed of film-forming agent, high efficiency corrosion inhibitor and base oil composed of a solvent dilution rust-proof oil. Compared with other types of anti-rust oil, wax film oil with thin film, rust and good, beautiful coating and so on.
2.3 Water-soluble anti-rust oil
China's current anti-rust oil are basically gasoline, kerosene or mechanical oil as a solvent, are from the oil fractionation of the product, the current can not be contained in the oil inside the aromatic hydrocarbon out, so gasoline, kerosene and machinery Oil contains aromatic hydrocarbons, the use of cars, kerosene as solvent oil, one of its low flash point, easy to fire, the second is pollute the environment, harmful to human health, water as a solvent D.K8 water solvent Rust oil does not contain aromatic hydrocarbons, lead and other harmful substances on the human body, the production of non-waste emissions, rust effect is also ideal, this anti-rust oil easy to apply, easy to use, used in the storage of fasteners on the rust , Can be used to wash water, this product has been identified by the relevant state departments to meet environmental requirements.
Rust level
1, wire brush rust - St
(1), St2 thoroughly manual and power tools rust surface should be no visible grease, dirt, scale, rust, paint coating and impurities.
(2), St3 very thorough manual and power tools rust with St2, but should be more thorough than St2 treatment, metal substrate was metallic luster.
2, sand blasting - Sa
(1), Sa1 mild sand blasting
The surface should be no visible grease, dirt, adhesion is not strong oxide, rust, paint coating and impurities.
(2), Sa2 completely blasting rust
The surface should be no visible grease, dirt, scale, rust, paint coating and impurities are basically removed, the residue should be attached firmly.
3, Sa2.5 level is very thorough sand blasting
The surface should have no visible grease, dirt, scale, rust, paint coating and impurities, and the traces of the residue show only spotted or striped slight stains.
4, Sa3 class sandblasted rust to the steel surface clean
The surface should be free of grease, dirt, scale, rust, paint coating and impurities, the surface has a uniform metallic color.
【Anti-corrosion】
Corrosion is a serious problem in the FGD system. It is also a problem that flue and chimney must face. On the world and China, the following types of anti-corrosion materials are mainly used for the corrosion of chimneys and flues.
(1) chimney anti-corrosion materials - FRP (FRP)
Because of the chemical corrosion of FRP and the cost is higher than that of high nickel alloy, many wetting system devices have achieved good effect by using FRP. According to foreign information, FRP has been successfully applied in the following aspects of wet desulfurization system: Absorption tower body, lime dissolution tank, collectors, defogger, slurry piping, flue, chimney.
② As the glass within the table smooth, not easy to scale, wear acid. So in the high flow rate and high concentrations of particulate matter in the region usually have a better effect.
FRP series of anti-corrosion materials in the domestic market are more common are: epoxy resin, modified with OM special anti-corrosion coating.
(2) chimney anti-corrosion materials - rubber
In the domestic market is more common with silicone rubber, polyurea. But the product is not high temperature, excellent waterproof and anti-acid performance is not conducive to long-term coal-fired unit
(3) chimney anti-corrosion materials - glass phosphor
As the glass filler is the main filler material SiO2, its temperature resistance, excellent acid resistance, in the market are more common are: foam glass tiles and glass scales
(4) chimney anti-corrosion materials - acid clay
① use
For wet desulfurization acid brick inner chimney liner corrosion. Coating temperature and acid resistance, strong adhesion, long life (more than 20 years), can withstand high and low temperature flue gas long-term erosion and rapid cooling conditions under the long-term effect is wet FGD after the release of the net Flue gas chimney lined with anti-corrosion special coating material.
② characteristics
KY2 acid-resistant clay coating is based on high-quality high-silica fume, dispersant, fixative and fine aggregates as raw materials, according to a certain proportion of scientific preparation, it has the following excellent features: excellent chemical resistance, high temperature wet corrosive Gas performance; very low water vapor permeability, hardening shrinkage is low, low linear expansion coefficient; can withstand high and low temperature flue gas long-term erosion and rapid quenching of the working conditions; excellent wear resistance; good adhesion ; Room temperature hardening, forming a simple construction, easy to repair.
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