Construction method and technical requirements of

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Construction methods and technical requirements of heavy-duty anti-corrosion coatings

construction methods and technical requirements of heavy-duty anti-corrosion coatings

May 22, 2019

I. preparation and requirements before painting

1 Before painting, the surface to be painted shall be treated, and the dirt shall be cleaned up. Painting can be carried out only after passing the inspection

2. The anti-corrosion coating shall have the product quality certificate, and the product shall meet the factory quality standard. Expired coatings can only be used after passing the inspection. If necessary, small samples should be tested

3. If different kinds of coatings need to be mixed and used, it should be determined by experiments. Different kinds of coatings cannot be mixed and used

4 When using thinner, its type and dosage shall comply with the standards of the paint manufacturer. When preparing the coating, it should be stirred evenly. If necessary, it can be used after filtering with a fine steel wire sieve

5. The welds of equipment and pipes must be painted after the heat treatment (when heat treatment is required), strength test and air tightness test are qualified

II. Sand blasting regulations

1 When sand blasting is adopted, proper measures shall be taken to prevent dust diffusion

2. The compressed air should be dry and clean, free of moisture and oil, and can be used only after passing the following inspection: put the white cloth or white paint board in the compressed air flow for 1 minute, and observe the oil, water and other stains on its surface with the naked eye. The filler of the air filter should be replaced regularly, and the accumulated liquid in the air buffer tank should be discharged in time

3. Abrasives should have a certain hardness and buffer toughness. Abrasives must be purified. The use of sheep should be screened. Not to mention natural sand containing oil stains, hard and ribbed emery, quartz sand, siliceous river sand, etc. should be selected, and its water content should not be greater than 1%. It is strictly prohibited to use sea sand

4. When sandblasting steel sheet, the abrasive particle size and air pressure should be adapted

5. When it is required to reach SA3 and SA2, river sand should not be used as abrasive

6. When the diameter of the outlet end of the nozzle is worn more than 20% of the inner diameter, the sandblasting nozzle should not be used anymore

7. Abrasives must comply with relevant regulations when they need important use

8. The stacking site and construction site of abrasives shall be flat and solid to prevent abrasives from being affected by moisture, rain or impurities

9. Threads, sealing surfaces and polished surfaces whose surfaces are not subject to sandblasting treatment shall be properly kept and shall not be damaged

10. During sand blasting, the metal surface temperature of the storage tank must be more than 3 ℃ higher than the air dew point temperature, otherwise the operation shall be stopped

III. construction regulations of coating

1 The quality of raw materials for coating anti-corrosion engineering shall comply with the provisions of relevant specifications

2. Putty, primer, intermediate transition paint, finish paint and finishing paint shall be used in accordance with the provisions of the design documents or product instructions. Different manufacturers and varieties of anti-corrosion coatings should not be mixed

3. The construction ambient temperature should be 5 ℃ - 38 ℃, the relative humidity should not be greater than 85% (except urushiol anticorrosive paint), and the temperature of the coated surface should be at least 3 ℃ higher than the dew point temperature

4. After the anti-corrosion coating is completed, it should be completely cured (curing period of more than 7 days) before it can be delivered for use

5. Outdoor construction should not be carried out in sandstorm, rain and snow

affected by many factors 6 The selection of anticorrosive coating varieties and the number and thickness of layers shall meet the requirements of design regulations

7. During the storage, construction and drying process, the anti-corrosion coating and diluent shall not be in contact with acid, alkali and water, and shall be dust-proof and sun proof, and fireworks are strictly prohibited

8. When the same paint is used for multi-layer coating, the same paint should be mixed into a certain color difference color to prevent missing coating

9. The construction of anti-corrosion coating of equipment and pipelines should be carried out after the strength test and air tightness test of equipment and pipelines are qualified. Before the test, the joint weld should be reserved, and the coating on both sides of the weld should be made into a ladder joint. After the test is qualified, it should be repaired according to the coating requirements of equipment and pipes

10. During coating construction, trial coating shall be carried out first

11. When using the paint, it should be mixed first. If there are crusts or other sundries, it must be cleaned before use. After the paint is opened, the remaining paint in the barrel must be sealed and stored; Mixed two-component paint must be used up at one time

12. The tools used for paint preparation and construction should be kept clean and cannot be mixed casually

13. If there are irregularities, weld ripple and non arc corners on the surface of the base course, putty matching the paint shall be applied. After the putty is completely dry, it shall be polished and leveled, and the primer construction shall be carried out after it is wiped clean

14. Most of the coating construction methods in the R & D stage can be high-pressure airless spraying or air spraying; Brush coating or roller coating can be used at the welds of the bottom plate

15. When brushing, the layers should be crisscross, and each layer should be reciprocated (except for quick drying paint) until evenly coated

16. During air spraying, the distance between the nozzle and the sprayed surface should be 250-350mm, and become 70 80。 The compressed air pressure should be 0.3mpa-055mpa. The pressure and other relevant parameters are selected according to the characteristics of coating products

17. During high-pressure airless spraying, the pressure should be 11.8mpa-16.7mpa according to the characteristics of the coating product. The distance between the nozzle and the sprayed surface is generally not less than 400mm

18. Brush coating, roll coating, more than 140 professors and experts from 15 colleges and universities, such as Central Nanjing University, central China Normal University, Xiangtan University and so on, will pre meet and make academic reports. The thickness should be uniform, and no omission is allowed

19. The number of coatings shall meet the design requirements, and the surface layer shall be painted along the medium flow direction. The surface shall be smooth without trace, with consistent color, and free of pinholes, bubbles, sagging and damage

IV. construction method of wear-resistant materials

1 After the completion of sand blasting and cleaning of the anti-corrosion parts, the primer shall be sprayed (brushed) twice first, and then the wear-resistant intermediate coat shall be plastered when it is slightly dry and does not touch the hand, so as to achieve smooth troweling, uniform thickness, no dew point, no air, move the limit rod hole up and down by hand, and then the second coat shall be plastered after the first coat is slightly solidified when the thickness is increased

2. When the intermediate coating is in the semi curing state, spray (brush) the surface wear-resistant coating, and brush the surface twice to make the surface smooth and free of bubbles

source: Oasis composite

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