The anti-corrosion coating of the thermal power fan is based on the corrosive environment and long-term use requirements of the fan, and should be listed as heavy anti-corrosion coating (also known as long-term anti-corrosion). Fan anti-corrosion coating, generally divided into primer, intermediate paint and topcoat. The main function of the primer is to prevent rust and enhance the adhesion between the metal surface and the intermediate paint; the main function of the intermediate paint is to enhance the thickness of the paint film and the texture of the paint; and the top coat has a decorative appearance, and more For a variety of functional requirements.
In recent years, in order to meet the needs of heavy anti-corrosion coating, there has been a thick-surface coating of the bottom surface. The high-pressure airless spraying technology can be used to spray a film of several hundred microns thick at a time. For the anti-corrosion coating of thermal power plant fans, after years of practice, our factory has gradually formed some coating matching systems suitable for long-term anti-corrosion coating of power station fans. In accordance with the state's requirements for environmental protection, it is an inevitable trend to install an exhaust gas desulfurization device in a new power plant. A commonly used desulfurization device uses carbon to absorb sulfur dioxide or sulfur trioxide in the exhaust gas. Therefore, the coating used in the desulfurization fan is resistant to alkali. It is the supporting scheme for the anti-corrosion coating of the wet desulfurization fan of Hengyun Power Plant.
Pre-treatment of the surface of the anti-corrosion coating process Shanghai coatings in the various aspects of the surface pre-treatment is the most important for the effectiveness of anti-corrosion coatings, must be fully considered. Our factory adopts the method of blasting and blasting mechanical rust removal, and selects and tests the abrasive. Abrasive particles are too small, which will affect the surface descaling level and efficiency. If it is too large, the shot blasting density is reduced, and a large pit is also caused.
The shot blasting is to make the surface of the steel rough, increase the surface area, improve the adhesion of the paint film, and improve the surface activation state. However, if the roughness is too large, it will consume too much paint and may trap the underside of the coating. Air bubbles or peaks that do not cover the coating, which can cause damage to the paint film and deteriorate the corrosion resistance of the paint film injection molding machine. According to the production experience of our factory, the surface roughness value of the power plant fan steel (including the combined value of the initial and secondary roughness) is 40-70 mixed m. When the thickness of the coating is about 200m, it is in accordance with the foreign data. The specification of the maximum roughness of 3 times.
In order to enable the surface treatment of the workpiece to achieve a better derusting quality and obtain a moderate roughness. The workpiece is sprayed and ejected by using steel balls and angular sand mixed abrasives. According to the data, the round particles are mainly used for tapping during spraying, while the angular particle abrasives are mainly used for cutting, which can make the substrate and the paint film bite and make the coating stronger on the substrate. Adhesion. After repeated trials and tests, the best mixing ratio of the spray-abrasive cold-rolled strip was selected. The rust removal level of the workpiece surface reaches the Swedish standard SaZ.5. The best combination of composition and ratio of mixed abrasives is: steel pellets 1 - 1.2; angular sand particles 1 - 1.4; angular sand: steel pellets = 3: 1.
The painting construction environment cannot be used for open-air painting in the hot sun and rain, fog and snow. Air relative humidity greater than 75% is not suitable for construction. The substrate temperature should be 3 ° C above the dew point. Direct sunlight in summer, the substrate temperature should be less than 40 ° C, when the winter temperature is below 5 ° C, it is not suitable for outdoor construction. It is impossible to apply when there is dust flying during the coating process and the drying process of the paint film.
The drying conditions and overcoating intervals of each coating of the paint shall be specified in accordance with the paint production unit. The composition ratio of the two-component paint must be accurate and cannot be ignored. For example, in polyurethane-based coatings, component A isocyanate (-NCo) is added in small amounts, and if it is insufficient to react with the base, the paint film is soft or sticky, and the water resistance and chemical resistance are decreased; If the amount of addition is too much, the excess (one NCO) base will absorb the moisture in the air and convert it into veins and carbon dioxide, making the paint film brittle and not resistant to impact.
The primer is sprayed with a metal substrate that has been sprayed and rusted. The cleaned air should be used to blow off the dust remaining on the surface. The primer should be applied in the shortest time. It should be painted within 24 hours under normal climatic conditions. complex. When using multi-canned zinc-rich primer, the ratio of each component should be accurate, fully mix thoroughly and use special thinner. The distance between the spray gun and the workpiece should not be too large, or when the temperature is high, use it properly. These high-boiling solvents prevent the solvent from evaporating too quickly, causing dry spray and causing the paint film to fall off.
When the top coat is sprayed with polyurethane paint, when the second layer of paint is sprayed on the surface of the completely dry paint film, the interlayer bonding force is deteriorated due to the high crosslink density, so the spray interval between the layers is It should be sprayed after the first layer of coating film, after 30 minutes or when the finger is dry, the ideal interlayer bonding force can be obtained. If the spraying interval of the coating is long due to manufacturing or installation and debugging, a re-coating type polyurethane coating with a small cross-linking density should be used to obtain a good bonding force between the coatings. The temperature difference varies greatly.
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