Anti-corrosive paint is a kind of paint that can be used on the surface of the object to protect the inside of the object from corrosion. It is a kind of paint commonly used in industrial construction. It is widely used in aviation, shipbuilding, chemical industry, chemical industry, oil pipeline, steel structure, bridge, oil drilling platform and other fields, and is favored by the majority of industrial engineering manufacturers.
1 species composition and characteristics
There are many kinds of anti-corrosion paint, according to the composition can be divided into: epoxy, polyurethane, acrylic, inorganic, chlorinated, rubber, polyethylene anti-corrosive paint; according to the use can be divided into: pipe, ship, metal, furniture, automobile, rubber; according to the solvent can be divided into: water-based paint, oil anti-corrosion paint;
Anticorrosive paint is a mixture of many aqueous silicate minerals, and the main chemical group is Al2O3 and SiO2 oxides. Al2O3 Mainly comes from clay minerals, SiO2 comes from clay minerals, but also comes from particulate quartz. The closer the Al2O3 content and Al2O3 / SiO2 ratio are to the theoretical value of kaolinite mineral, the higher the purity of such clay is.
It can be used in harsh conditions, and has good durability, weather resistance, can be used in the ocean, underground and other harsh conditions for 10 years or more than 15 years, even in acid, alkali, salt and solvent medium, and under certain temperature conditions, can also be used for more than 5 years.
The more kaolinite content in the clay, the better its quality. The higher the refractoriness of the clay, the wider the sintering and melting range of the clay. The main impurities in the clay are alkali metals, alkali soil metals, iron, titanium and other oxides, and some organic matter. All oxides play a melting role and will reduce the fire resistance of raw materials. Therefore, the lower the impurity content in clay, especially the content of Na2O and K2O, the higher the fire resistance. There are many kinds of clay minerals, but usually only composed of 5~6 minerals, the main mineral is kaolinite. Common impurity minerals are quartz, water mica, iron minerals, feldspar, rutile and so on. The impurity content and uniformity of distribution affect the fire resistance of clay. Anticorrosive paint will have a series of physical and chemical changes, such as decomposition, combination, recrystallization, etc., accompanied by volume shrinkage. These changes have an important influence on the process and properties of clay products. China's clay raw materials, whether hard clay, soft clay or semi-soft clay, are mainly kaolinite type. Therefore, the heating change of clay is essentially the heating change of kaolinite and the physical and chemical reaction between kaolinite and impurity minerals. Hard clay clinker is the main raw material of clay refractory, which is usually calcined in hard clay kiln, or rotary kiln or vertical kiln.
In addition to the chemical composition, the production of refractory materials requires high clay clinker volume density, low porosity, low water absorption rate, and full sintering. Therefore, the calcination temperature and insulation time have obvious influence on the quality of clay clinker. When the calcination temperature is 1200~1250 degrees Celsius, the clinker volume density and porosity index are the best. At greater than 1350 degrees Celsius, the volume density decreases and the pore rate increases, because a large amount of square stone is generated at this time, the volume expands, at the same time, the coke gem layer develops in the clinker block cracking, the main mineral phase of anti-corrosion paint hard clay, accounting for 35%~55%, followed by the glass phase and square stone.
2 Varieties
Epoxy series
Epoxy anticorrosive paint series: epoxy zinc rich primer over vinyl chloride anticorrosive paint epoxy bottom paint epoxy coal asphalt anticorrosive coating epoxy cloud iron intermediate paint
Epoxy paint is usually used as primer and intermediate paint for corrosive paint.
Epoxy anti-corrosion paint: it is composed of epoxy resin, anti-rust pigment, filler deployment, need to add another curing agent.
Epoxy anti-corrosion paint characteristics: water resistance, acid and alkali resistance, good rust resistance performance. With iron and steel, cement surface adhesion relay is strong.
Epoxy anti-corrosion paint use: suitable for pipeline, all kinds of steel structure, bridge, petroleum brick well platform and chemical equipment, water resistance, oil resistance, chemical resistance reagent, for protection base, can also be used for cement substrate base or bottom surface integrated protection.
Polyurethane series
Composition of polyurethane anti-corrosion paint: two component self-drying paint, one is polyester color paste, and two is special curing agent.
Characteristics of polyurethane anti-corrosion paint: good anti-corrosion performance. The coating has good adhesion, toughness, wear resistance, elasticity and acid resistance, alkali resistance, salt resistance, oil resistance, petroleum products, benzene solvents and water resistance, boiling water resistance, sea water resistance and chemical atmosphere resistance.
Application of polyurethane anti-corrosion paint: suitable for anti-corrosion coating of steel structure facilities, natural gas pipeline, chemical facilities, oil tank tank, bridge, wharf, gas tank, motor, electrical appliances, aluminum alloy, etc.
Oleic series
Acrylic acid anticorrosive paint composition: acrylic resin as the main base material, with modified resin, pigment, filler, additives, solvent and other anticorrosive paint.
Characteristics of acrylic anti-corrosion paint: paint film has excellent light and color protection and weather resistance. It has very good physical and mechanical properties. The paint film is dry and fast, the construction is convenient, and it can be constructed under-20℃ - -50℃ temperature conditions.
Use of acrylic anticorrosion paint: this paint is suitable for anticorrosion protection and decoration of steel structure and concrete.
Vinyl perchloride anti-corrosion paint
Composition of vinyl chloride anticorrosive paint: the paint is made up of vinyl chloride resin, alkyd resin, toughening agent and pigment after grinding, and then add mixed solvent modulation
Characteristics of vinyl chloride corrosion paint: the paint has excellent corrosion resistance, acid and alkali resistance, mildew and moisture-proof, poor adhesion, such as good matching, can make up for.
Use of supervinyl chloride anticorrosive paint: used for all kinds of chemical machinery, pipes, equipment, construction and other metals and wood surface, can prevent the corrosion of acid, alkali and other chemicals.
Chlorinated rubber anticorrosive paint
Chlorinated rubber corrosive paint composition: chlorinated rubber, modified resin, pigment, filler, stabilizer, organic solvent, etc
Chlorinated rubber anti-corrosion paint characteristics: with good acid resistance, salt corrosion performance and atmospheric corrosion resistance performance, and has good physical and mechanical properties.
Application of chlorinated rubber anticorrosive paint: mainly used for protective coating of automobile chassis, construction machinery chassis, or protective coating of equipment, pipelines and metal components under mild erosion.
Hyperchlorinated polyethylene
Hyperchlorinated polyethylene anticorrosive paint composition: chlorinated polyethylene dilute resin (HCPE), modified resin, plasticizer, pigments, additives, solvents, etc
High chlorinated polyethylene anticorrosion paint performance: paint film tough, with excellent weather resistance, corrosion resistance and flame retardant. It has excellent anticorrosion performance for industrial atmosphere, "three wastes" pollution media and different concentrations of acid, alkali, salt, mineral oil and other corrosion media (ammonia, chlorine, carbon dioxide)
Use of overchlorinated polyethylene anticorrosive paint: suitable for petrochemical industry, metallurgical mines, construction workshop, transportation facilities, ship bridge, construction machinery, sewage treatment and other steel structure and concrete facilities, industrial floor and other anti-corrosion engineering.
Inorganic anticorrosive paint
Inorganic corrosion paint by new inorganic polymer and after dispersed activated metal, metal oxide nanomaterials inorganic polymer coating, can rapid reaction with the surface of steel structure, generate with physical and chemical protection, no pollution to the environment, long service life, anticorrosion performance reached the international advanced level, is a high-tech replacement products that meet the requirements of environmental protection.
3 Construction
Surface pretreatment
If there are impurities, oil, grease and dirt, the surface shall be cleaned according to the cleaning method specified in the Specification for Steel Surface Pretreatment before Painting SY / T0407.
Steel surface shall be sprayed according to the method specified in SY / T0407. When spraying, it should be carried out in the order of top, wall and bottom. The rust removal quality shall reach the Sa 2.5 level specified in GB / T8923- -1998. The anchor grain depth shall be selected according to the anti-corrosion grade, and the ordinary type is about 40 μ m. Select 6-8mm nozzle, compressed air pressure at nozzle inlet 0.5-0.6Mpa, injection angle 30-75, incident distance 100-200mm and sand grain size 0.8-4 mm. When blasting with thin steel sheet, the sand particle size and air pressure should be appropriately reduced. When the wear amount of the sandblasting outlet end and diameter exceeds 1 / 2 of the starting inner diameter, the nozzle shall not be used further. The Surface pretreatment of the accessories shall be the same as for the main parts.
After injection treatment, the surface shall be cleaned with dry, clean and oil-free compressed air.
After rust sting, the defects exposed on the steel surface and weld must be treated.
Safety measures: maintain ventilation to keep the solvent gas concentration below the dangerous concentration, and the spraying operators should wear protective clothing and masks, and clean up immediately after contacting the nose when spraying.
Coating preparation
If the anticorrosive paint is A two-component paint, the two components can be mixed before coating, and confirm whether components A and B are matched, whether they are consistent with the required coating model, and whether it is invalid.
Compounding of components A and B must be stirred until the bottom has no deposition and is uniform up and down.
Prepare A small amount of uniform components A and B according to the proportion required by the instructions, and adjust the viscosity with A special thinner to achieve the best coating process conditions, and ensure the thickness and quality of the single film.
Calculate the amount of components A and B according to the coating area and the thickness of the single film, and control the mixing amount to be up within 6 hours to prevent too much mixing and thickening of the coating from affecting the quality of the coating.
The dosage of coating special thinner should be controlled to not exceed 15% (spraying) or 8% (brush), add component A according to the calculated proportion to calculate evenly, and then add component B to stir for 10-15 minutes, mature components A and B, and finally stand for 15-20 minutes to eliminate the air bubble introduced by mixing. The length of stirring and standing time depends on the amount of ingredients.
The mixed coating can be filtered with a 100-mesh filter before spraying. In the spraying process, once the coating is excessively reacted and thickened, stop spraying immediately. If the coating is scrapped, it should be remixed. The excessive reaction time of coating is related to the ambient temperature, the time required for high temperature is short, the material should be matched less, while the low temperature is long, the amount of ingredients is appropriately increased.
Brush process
The specific construction should be prepared according to the structure of anti-corrosion materials and the measures to ensure the quality of anti-corrosion layer.
The environmental conditions when painting shall comply with the requirements of the manual. In case of rain, snow, fog, sand and other climatic conditions, the open construction of anti-corrosion layer should be stopped. When the construction environment temperature is lower than-5℃ or higher than 40℃, or the relative humidity is higher than 80%, it is not suitable for construction. Uncured anticorrosive layer shall prevent rainwater from soaking.
If the surface pretreatment occurs during the interval between the first primer, the rust part shall be pretreated again before painting. And timely coating brush construction, to prevent rust return again.
Chlorinated sulfonated polyethylene anti-corrosion paint can be applied without gas spraying, gas spraying, brushing or roller coating and other construction methods, according to the order from top to bottom, brushing should be uniform, not leakage, which coating method should be decided according to the anti-corrosion construction scheme. The brushing operation shall meet the following requirements:
A. When using the brushing method for construction, the application force should be uniform and brush in the same direction to avoid surface lifting.
B. When spraying, the spray gun should move evenly, and keep the nozzle perpendicular to the spray surface.
C. When using the roller coating method, the roller dip material should be uniform, not too much, the roller coating force should be uniform, and should not be too large, and should maintain a uniform speed; the roller should be rolled in the same direction, each direction can be different. The corners, accessories and other parts where the drum cannot be painted should be recoated with brushing tools.
Welds, corners and surface uneven parts should be dipped in paint or increase the number of brush.
The brushing interval of each paint should not be greater than 24 hours, and the next paint should be painted after the upper paint table is dry. If the last paint has been solidified, should be painted after the next paint. After the last finish coating, it should be cured at 25℃ for more than 7 days before being put into use. If the curing temperature is less than 10℃, it should solidify for more than 10 days before putting into use.
During the construction process, the paint film thickness of the coating should be measured in different parts, and the coating viscosity and coating process parameters should be adjusted in time to ensure that the final thickness of the anti-corrosion layer meets the design requirements.
4 Precautions
Before the construction of anti-corrosion paint, we must pay attention to two points, one is the danger to human health; the other is the danger of explosion. The safety regulations of the products should be understood before the paint construction. For example, the acrylic engineering primer and the acrylic engineering paint, although only a word difference, the function is similar, but in the ratio, use is not the same, need to pay attention to. If confusion occurs, once an accident occurs, it will harm human health.
5 Development trend
1. Develop water-based anticorrosion primer and topcoat for steel structure
Water-corrosion primer must solve the problems of substrate corrosion and poor water resistance.
The application of some new emulsifier-free emulsion has fundamentally improved the problem of poor water resistance, and the problem of construction function and application function should be solved in the future.
As a top paint, it is mainly under the condition of ensuring the protection function, to improve its decorative nature and durability.
2. Develop a high-solid and solvent-free preservative coating series
China's products are mainly in the technical level, economic strength, quality assurance system and product reputation and other comprehensive strength and foreign business gap, it is difficult to enter the market.
To this end, efforts should be made in technical development, especially the development of lead-free and chromium-free primer, that is, zinc phosphate and aluminum phosphate.
3. Develop a water-based zinc-rich primer
Inorganic zinc rich primer and water-based inorganic zinc rich primer are one of the long-acting primer, but they are both solvent-based coatings.
The water-based inorganic zinc-rich primer with high modulus potassium silicate as the base material is a high-function anti-corrosion coating tested by practice, which has the development potential.
4. Develop normal temperature curing heat-resistant and anti-corrosion coating for heat exchanger
Heat exchanger requires an anticorrosion coating with high heat resistance and high thermal conductivity efficiency. The epoxy amino coatings used needs to be cured at 120℃ and requires multiple coatings cannot be used in large devices.
5. Develop coatings that can cure at room temperature and facilitate construction
The key is to get the best balance between the anti-corrosion function, the heat transfer function and the construction function of the coating.
6, the development of chlorinated rubber series of anticorrosive coating substitutes
Because chlorinated rubber is a single component, the construction is convenient, water resistance, oil resistance, atmospheric aging resistance function is excellent, in the ship, industrial anticorrosion and other fields, has a broad market.
However, because of the production of chlorinated rubber using CC1 as a solvent, destroy the ozone layer. Therefore, the industrial developed countries have developed their alternative products. More successful are German BAST MP chloroether resin series, water eous chlorinated polyethylene or modified products.
7, develop scaly anti-corrosion coatings
Mica iron oxide (MIO) has excellent dielectric resistance, atmospheric aging resistance and blockade function, as a primer and top coat in Western Europe.
There is a certain gap between domestic MIO and foreign products in terms of particle size distribution, diameter and thickness ratio, density and so on. Similar problems exist in the development of glass-scale coatings.
8. Develop organic and modified inorganic anti-corrosion materials
Organic emulsion modified concrete is used abroad to improve its strength, medium resistance, and is widely used in industrial floor coating.
Among them, epoxy water emulsion (or solvent type epoxy) is the fastest development, which is called polymer cement.
