General coating

The surface of the equipment that needs to be painted should undergo strict surface treatment according to the regulations of the Steel Structures Painting Council (SSPC) or other equivalent standards in the United States. The paint should be selected correctly and the painting process should be carefully followed. The quality of surface treatment must be strictly inspected, and painting is not allowed if it does not meet the requirements specified in the standards.

The application of paint should comply with the requirements specified in this article. Limitations during painting: If the painting of the equipment is carried out in the contractor's factory, the contractor must ensure that such conditions exist: good surface cleaning has been carried out, there is no dust in the atmosphere, good ventilation and lighting, and there are appropriate temperature and humidity conditions. For material painting work carried out outdoors, do not carry out painting work in harsh weather conditions such as high humidity and strong winds. Unless appropriate measures are taken to overcome these difficulties. During surface treatment and painting, the surface temperature to be treated must be at least 3 · C above the dew point of the surrounding air before proceeding. When painting, the temperature of the treated surface should not be lower than 7 · C and not higher than 38 · C.

Moisture and humidity limitations

Outdoor painting operations cannot be carried out under scorching sun or in rainy, snowy, or foggy weather; Paint should not be applied in smoke or when the relative humidity is due to changes in metal temperature and ambient air temperature causing paint to solidify on metal surfaces. Unless otherwise specified and recommended by the paint manufacturer, painting should generally be carried out under conditions of relative humidity below 85%. All surfaces should be completely dry before and during painting, as well as within 24 hours after painting.

time limit

Generally, the primer should be applied to the sandblasting area within 4 hours after the sandblasting treatment is completed. If this time is exceeded, the surface should be treated again. This time limit can be modified to 4 hours or more depending on the implemented temperature and humidity control. The main standard should be that no rust film has formed on the surface before applying the primer. If any rust film forms, the surface should be sandblasted before applying the primer. The interval between painting should be strictly controlled according to the painting process.

Temperature limit

Unless otherwise specified and recommended by the paint manufacturer, painting should generally be carried out under conditions of 10 ℃ to 32 ℃. Painting should not be carried out when the ambient temperature is below 5 ℃ or when the temperature is expected to drop to 0 ℃ before the paint dries. Steel with a temperature above 50 ℃ should not be painted unless specially formulated paint is applied at that temperature. When steel is painted in hot weather, preventive measures should be taken to ensure that the specified dry film thickness of the paint is obtained. The welding area can only be painted after 72 hours of welding. Construction can only be carried out when the substrate temperature is 3 ℃ above the dew point. Do not apply paint when there is condensation on the surface. The interval between painting should be strictly controlled according to the painting process.

Clean air

During the painting and film drying process, the surrounding air should be kept clean, and painting should not be done in an environment with dust.

Mixing of paint

The blending of paint should strictly follow the product instructions of the paint manufacturer. The certificate of conformity of the paint should be strictly inspected, and unqualified and expired paint should not be used for painting. Before use, the paint must be mixed and thoroughly stirred according to regulations to ensure thorough mixing. When performing layered coating, the color of each layer should maintain sufficient contrast to check if the surface is fully covered.

Painting method

High pressure airless spraying method can be used for construction, as well as brush coating or compressed air spraying method. Brushing: When brushing, dip the paint brush in an appropriate amount of paint, distribute it over a considerable surface area, first expand horizontally, and then straighten vertically to ensure even distribution of the paint. You can also expand vertically first and then streamline horizontally, gradually and without omission. Compressed air spraying: Compressed air spraying is the process of using compressed air to attract (or compress) paint from a pot shaped container to a spray gun. At a pressure of 0.2-0.5Mpa, the paint mixes with air and atomizes at the spraying point, and is sprayed onto the surface to obtain a uniformly distributed coating. Coatings used for compressed air spraying are thinner than those used for brush and roll coating, so a portion of diluent needs to be added to general coatings. High pressure airless spraying: High pressure airless spraying usually uses compressed air to drive a high-pressure pump, which sucks in and pressurizes the coating to 10-25Mpa, passes through a high-pressure hose and spray gun, and finally sprays out through an olive shaped nozzle. When the paint leaves the nozzle, it is atomized into very fine particles and sprayed onto the surface to form a uniform coating film. Other requirements: To ensure the thickness of the paint film on welds, edges, corners, and other areas, a pre coat should be applied with a paint brush before conducting large-area airless spraying.

Paint repair

Coatings damaged during transportation or construction, bolt heads and nuts installed on site, and welding surfaces must be repainted. Before repairing, the surface oil stains must be cleaned with solvents and rinsed with clean water. After completing the specified surface treatment, the repair work can be carried out by applying one layer of primer and one layer of intermediate paint. The paint repair requirements are the same as before. All primers, intermediate paints, and topcoats should be provided by the same paint factory and ensure that the performance of these paints matches each other. Unpainted steel surfaces in the factory should be coated with anti-corrosion materials approved by the purchaser for temporary surface protection. All paints delivered for use on site must be in their original packaging at the time of delivery, with complete names, instructions, and storage periods. Use solvents to clean or sandpaper to smooth all repair primers and inner coatings on equipment and other visible surfaces.