Procedure of coating inspection

In the construction stage of the project, coating inspection shall be carried out in strict accordance with the following standard steps: inspection of steel used, inspection of shop primer construction, inspection of steel treatment (welding, free edge cutting, etc.), surface treatment inspection, coating inspection before and during construction, quality inspection after coating construction, inspection of steel treatment Huicong coating network news: in the construction stage of the project, coating inspection should be carried out in strict accordance with the following standard steps: inspection of steel used, inspection of shop primer construction, inspection of steel treatment (welding, free edge cutting, etc.), surface treatment inspection, coating inspection before and during construction, quality inspection after coating construction, inspection of steel treatment 。 When building a new ship, or when the repair project includes steel replacement or surface sandblasting, the following inspection must be carried out for the steel involved: grinding the rough weld to remove the rough weld smoothly / grinding the weld spatter to check whether there is fracture and pitting; checking whether there is surface defect such as "lamination" and surface treatment The inspection of surface treatment includes the following items: cleanliness; cleaning with solvent and removing salt, grease and dust Assessment of current surface rust grades assessment of surface condition (surface preparation grades and roughness) to assess whether the surface residual contaminants are within acceptable limits The international standard iso8501 (- 1) is an important standard for the inspection of steel structure and surface treatment The surface condition of steel is evaluated by four corrosion grades, a, B, C and D Photographs are usually used to show the actual grade of the steel surface In addition to the differences between grades A, B, C and D, 24 pictures are attached to the standard to show the visual cleanliness of the steel surface after mechanical treatment with wire brush, sand blasting and flame cleaning respectively Many methods can be used to measure the surface roughness Among them, the most suitable method for field use is to use a sample plate for measurement According to the international standard iso8503, this method adopts two comparative sample blocks, one is suitable for the effect of blast cleaning with steel sand (refer to sample g), the other is suitable for the surface effect of blast cleaning with metal steel shot (refer to comparator s) Three roughness specifications can be determined by the above reference sample: fine, medium and coarse A simple test for degreasing / greasing of contaminated surfaces is the "discontinuous water film test method" in which a drop of water is dropped on the treated surface If there is no oil / grease, the water drop will spread rapidly on the surface, and if there is oil / grease, the water drop shape will be formed on the surface This approach is not a standard The most commonly used method to detect water-soluble salt is to dissolve the salt existing on the surface, and then measure the conductivity of water sample Conductivity is an indicator of the conductivity of a solution Its unit is "Siemens" (?? s) The conductivity can be converted to the corresponding surface salt content by calculation The methods for detecting the total amount of soluble salts on the surface are as follows: sampling method is in accordance with iso8502-6, sampling soluble pollutants analysis, and Bresle sampling method The analytical method is based on iso8502-9 Inspection before and during construction inspection before and during construction: the inspection of climatic conditions must follow the product technical specification to ensure the correct mixing and dilution (especially important) to measure the number of wet film thickness (WFT) coating layers In the coating specification, the drying time (the shortest drying time and the longest drying time) between the wet film thickness (WFT) coating layers shall be explicitly measured Pay attention to the control of the equipment and methods used The wet film thickness wet film thickness meter (iso2808) is a practical tool for measuring the wet film thickness of plane (surface) When measuring the second film, the first film becomes soft, or the first layer is a soluble coating, the measurement results of the second coating thickness may be affected The relative humidity suspension hygrometer (iso8502-4) consists of two thermometers, one is to measure the dry temperature and the other is to measure the wet temperature (the sensor is wrapped with wet cotton wool) When the hand is rotated, the moisture in the cotton wool evaporates, so the reading ratio of the thermometer with lower temperature and the dry thermometer for measuring the air temperature is obtained, and the relative humidity can be calculated according to the temperature reading Dew point temperature dew point is the highest temperature at which moisture in the air condenses If the subsequent climatic conditions are suitable for painting work, it is necessary to determine the dew point It can be calculated according to the list or dew point calculator At present, there are two slightly different types They are designed according to the similarity principle, including two tags, which can be set mutually, so as to read the required information When you have measured the dry and wet temperatures, you can read the dew point and relative humidity from the dew point calculator Steel temperature contact thermometer is an electronic instrument used to measure the surface temperature of steel When the measured steel surface temperature reaches the dew point, you can decide whether to start painting or not The steel surface temperature shall be higher than 3 OC above the dew point before coating construction Inspection after construction and inspection after coating is another very important stage The inspection after coating includes: dry film thickness (DFT) curing time / drying time; the most commonly used equipment for testing dry film thickness through adhesion pinhole is electromagnetic dry film thickness gauge Magnetic dry film instrument is a simple tool, and its measurement is not very accurate The tool shall be calibrated to zero and the approximate thickness measured At present, there are many types and functions of electromagnetic dry film instrument available for selection The pull-out test of adhesion according to the international standard iso4624: stick the pull-out cap to the coating surface, and then pull it with external force until the pull-out cap breaks away from the coating Then measure the external force used A variety of drawing tests are available This test is a destructive test, which means that the test will damage a small part of the paint film.