In order for the coating to protect the steel components for a long time, it is one of the important factors that the coating film is uniform and reaches a certain thickness. Thickness management includes specifying the average thickness or minimum thickness that needs to be achieved, controlling the thickness, and carrying out regular Check and measure the child, and repaint the parts where the thickness does not meet the requirements to make it reach the specified thickness. The specified film thickness can be expressed as an average or a minimum value. According to this regulation, the thickness of any part shall not be lower than the minimum value.
In actual painting, the thickness is often uneven, but the average thickness needs to be a minimum value. In other words, the minimum value of the actual measured thickness needs to be more than 90% of the specified average value. For anti-rust coatings, This is especially important.
Thickness is measured by the amount of wet film and dry film. The purpose of wet film measurement is to better achieve a uniform dry film thickness, so as not to be too different from the specified value.
Some paint instructions specify the wet film and dry film thickness. When painting, the wet film thickness needs to reach the specified value, and the dry film thickness is also close to the specified value after drying. If the paint specification does not indicate the relationship between the wet film and dry film at the same time, but only indicates the solid content, the measured wet film thickness can be used to calculate the film thickness according to the following formula
Id=Iwn/100
In the formula, Id——dry film thickness (µm),
Iw—wet film thickness (µm),
n——solid content (%).
Painters must carry a Nirvana meter with them, and measure the thickness of the wet film immediately after spraying a few guns before spraying, to see if the Spray Gun can reach the specified thickness, so that they know what to expect. During the spraying process, they should also Measure frequently and respray immediately where the wet film thickness is insufficient. Solvents and thinners evaporate quickly and the thickness will decrease quickly. If you do not measure it immediately, the wet film thickness obtained will be low. In the thinnest coating film and the solvent evaporates quickly, the measurement results will be very bad. Accurate, the film thickness is estimated from the wet film thickness of Lide, a reasonable and accurate method is to get the wet film thickness immediately after spraying
Dry film consumption can be done by destructive method or non-destructive method. The most destructive method is to remove a small piece of paint skin with a knife, or scoop up a small piece of paint film from the bottom, and then use a scale gauge or paint Tester to remove the amount of dry film. Advantages, this method can measure the total thickness of the coating film system. If the color of each layer is different, the thickness of each coating film can also be measured separately. The disadvantage of the destructive method is that the damaged part needs to be inspected. To repair the paint film, it is necessary to fill up all the paint one by one, and it takes time.
Non-destructive measurement is performed with a magnetic thickness meter or a non-magnetic bamboo thickness meter after the coating film is effectively dried to measure the arithmetic mean of each point (at least 3 points), which is the average thickness of the coating film. The average thickness of the coating film can be calculated according to the number of coatings used and the area of the object to be coated, but I, <Considering the loss of coatings, there are many reasons for the long-lasting coatings. When painting on a large area (with a brush), the coating The loss may be less than 1%. When spraying the general cabin, the paint loss is 30%. When spraying the complex structure exterior or superstructure, the paint loss is 10½ pieces. When spraying linear objects, the paint loss can reach about 80%. At present, the solid content and coating density need to be known. These data are generally explained in the coating manual. The average film thickness can be calculated by the following formula
Jd = (100-X/100)×10nG/ρA
In the formula, Id---ten film thickness (µm),
X - paint loss (percentage of total paint used);
n——solid content of coating (%)
G - the total number of paint used (kg)
A - the area of the object to be coated (m 2 )
ρ ——Density of paint (g/cm 3 ).
杨庆臣 - 《北京化工大学》
蜈蚣 - 《南北潮商城》