Construction quality inspection report of China National Fire Protection and Building Materials Association (cs2202312); inspection report of national fire protection construction engineering construction quality control standard (cs22195-20064); construction quality inspection report of China National Fire Protection and construction materials Association (cs23064).

 Construction process flow chart of fireproof coating for steel structure engineering

 （1） Construction process and technology 

 　　1.Surface treatment of base course

 　　A. If the surface of steel structure is not coated with antirust paint, it shall be antirust and oil stain removed, and its surface anti rust grade shall not be lower than ST2 grade. 

 　　B. After the rust removal of the steel structure surface meets the requirements, the first coat of antirust paint shall be applied within 4-6 hours, and the antirust paint shall be applied according to the anti-corrosion standard. 

 　　C. If the surface of steel structure has been coated with antirust paint, the surface shall be cleaned of oil and floating ash. 

 　　D. If anti rust paint is applied on the surface of steel structure which is unconventional or needs to be treated according to the special requirements of the project, one course of interface agent can be applied to make the fireproof coating completely compatible with the anti rust paint on the surface of steel structure, so as to enhance the bonding strength.The antirust paint applied in this project does not react with the selected fire retardant coating, so there is no need for interface treatment. 

 　　2. application of fire retardant coating

 　　A. Preparation for painting antirust paint: 

 (1) Open the barrel: check the name, model and color of the coating to see if it is consistent with the design regulations or selection requirements, and check whether the manufacturing date exceeds the storage period. Otherwise, it shall be dealt with separately.If the coating is found after opening the barrel, all the paint skins should be taken out instead of mixing them into the paint, so as to avoid affecting the quality. 

 (2) Mixing: due to the different proportion of each component in the coating, sometimes there will be precipitation, so before use, the paint and sediment in the barrel must be mixed evenly with a mixer before use. 

 (3) Dilution: when the coating leaves the factory, the viscosity of the coating has been adjusted to the viscosity range suitable for the construction requirements. It can be used after opening the barrel and mixing. However, due to the influence of different conditions such as storage conditions, construction methods, working environment and air temperature, it is sometimes necessary to use diluent to adjust the viscosity. At this time, special diluent can be used for dilution, and the addition amount should not exceed 30%. 

 　　B. The environmental conditions for the application of fire retardant coating are as follows: 

 (1) Working site: the painting work should be carried out indoors as much as possible, and the environment should be kept clean and dry, so as to prevent any surface that has been painted to be adhered by dust, water drops, welding spatter or other dirt and affect the quality. 

 (2) Ambient temperature: the ambient temperature during construction is generally controlled between 5-38 ℃ (refers to the whole process from coating construction to coating drying and curing). 

 (3) Relative humidity: the relative humidity should be controlled below 90% in painting construction, and the surface temperature of steel members can also be controlled higher than the dew point temperature.When there is condensation on the surface of steel components, it is not suitable to operate. 

 (4) When spraying for more than 5 hours, it is not suitable to use in other aspects.In addition, the steel components need to be welded at the installation site, the specified length shall be reserved according to the standard, and no fire retardant coating shall be applied. 

 　　C. Application of fire retardant coating 

 Thin steel structure fire retardant coating (water-based) is sprayed, and ultra-thin steel structure fire-retardant coating (oily) is applied by brush.The painting process should be from top to bottom, from left to right, from inside to outside, from difficult to easy, crisscross.According to the fire rating standard and the inspection report of fire retardant coating proposed by the design and fire department, the coating thickness and coating number are determined, i.e. steel column 2.5h = 3.4mm, 8-9; steel beam 2H = 2.17mm, 7-8; purlin and support 1.5h = 1.68mm, 6-7.

 (1) Application of ultra thin fireproof coating for steel structure

 (1.1) before painting, check whether the base material has been coated with antirust paint. In case of missing brush and falling off, relevant personnel shall be informed to make up the brush before construction. 

 (1.2) the paint shall be mixed evenly before rolling or brushing. The thickness of each time shall be no more than 0.3 mm, and there shall be no sagging. 

 (1.3) before using the spray gun for operation, adjust the air compressor pressure to ≥ 0.4MPa, the muzzle of the gun is 20-30cm away from the working face, and the thickness of each pass is ≥ 0.3mm. When the wind force is greater than level 4 on that day, spraying shall be stopped and other methods shall be used to avoid waste. 

 (1.4) after the surface of the previous coating is dry, the next construction shall be carried out until the required thickness is met. 

 (1.5) the construction environment temperature is 0-35 ℃, and the relative humidity is less than 90%. When the wind speed is higher than level 5, rainy days or there is condensation on the surface of the components, it is not suitable for construction. 

 (1.6) in the process of spraying components, protective measures shall be taken for other components to avoid pollution. 

 (1.7) the coating is not inflammable and explosive, and has no pollution, and can be transported as general goods. 

 (1.8) store in a ventilated and dry environment, and the temperature can be below 35 ℃. 

 (2) Application of fire retardant coating for thin steel structure

 　　(2.1) before operation, check whether the components have missed the anti rust paint, and remove the floating soil and welding slag.

 　　(2.2) spraying method shall be adopted for construction, the distance between spray gun and component shall be ≤ 30cm, air compressor pressure shall be more than 0.54mpa, and thickness of each pass shall be no more than 2mm.

 　　(2.3) when using the coating, stir it evenly. If it is too thick, tap water can be added slightly, with the addition amount less than 5% / barrel

 Too much, or lose adhesion, affect adhesion.

 　　(2.4) there should be no rain and condensation in the construction environment. The wind force should be less than grade 4 and the temperature should be 5-35 ℃.

 　　(2.5) the surrounding area shall be covered during spraying to avoid pollution.

 　　(2.6) when spraying again, check the previous one and spray the next one after the surface is dry.

 　　(2.7) the storage temperature is 5-40 ℃. It is not allowed to be exposed to the sun, but can be transported as general goods.

 (3) The interval time between the front and the back courses should be controlled within 8-10 hours, that is, after the coating is dry, the latter can be applied. 

 (4) The thickness of the fire retardant coating is: 2.5h (waterborne): 3.4mm; 2.0h (oily): 2.17mm; 1.5h (oily): 1.68mm. 

 　　D. Painting and repair of fire retardant coating: 

 (1) When the steel members are packed, stored, transported, welded and corrected at the construction site, it is inevitable that some paint film will be damaged and damaged, which must be repaired.In addition, some parts need to be repaired after installation on site.

 (2) In order to ensure the smoothness of the repair film, the paint film should be repaired within a distance of 10-20cm around the defect to make the film have a certain slope.

 (3) Repair according to the original coating painting process requirements and procedures. 

 （2） Quality control: 

 The quality of fireproof coating for steel structure directly affects the coating effect and service life.The coating is a semi-finished product, which must be applied to the surface of steel members through construction. Only after the film is formed can it play a role of fire protection. Therefore, in addition to strengthening the quality control of the whole process of painting preparation, construction environment conditions, construction methods, repair and repair coating, the following aspects need to be controlled:

 (1) Construction must be carried out by personnel who have received professional training and obtained work license. 

 (2) The painting quality should be controlled according to the amount of application. 

 (3) The inspection results on the surface of the component to be painted and the inspection results after the completion of each painting process shall be summarized.The summary contents include working environment temperature, surface cleanliness, brushing times of each layer, coating type, ingredients, dry film thickness, etc. 

 (4) Check that the surface quality of the brush should be uniform and meticulous; no obvious color difference; no sagging, loss of gloss, wrinkling, pinholes, pores, rust, cracks, peeling, dirt adhesion, missed coating, etc.; good adhesion.