In addition to protection and achieving certain functional indicators, the purpose of the coating almost always requires a certain appearance quality, especially decorative coatings or protective decorative coatings. They all require a gorgeous and light-resistant appearance, and are not allowed to exist Obvious flaws. Therefore, the appearance inspection of the coating is the most basic and commonly used inspection content. If the appearance is unqualified, there is no need to conduct other tests. Therefore, appearance quality inspection is one of the most important and common items in coating quality inspection.
Coating appearance quality includes:
(1) Surface defects such as pinholes, pitting, nodules, bubbles, burrs, spots, burnt, shadows, yin and yang sides, and tree
(2) Roughness refers to the smoothness of the surface of the product after coating. During appearance inspection, the roughness should reach or be lower than the specified roughness index.
(3) Gloss The reflectivity of the surface of the product after coating. During appearance inspection, its glossiness should meet or exceed the specified glossiness index.
(4) Coverage refers to whether the part that should be coated is completely covered by the coating after the product is coated.
(5) Color Except for silver-white coatings, for various colored coatings, the specified color should be achieved during appearance inspection.
Sampling for coating appearance inspection shall be carried out according to product requirements or inspection standards. Usually, there are several sampling methods as follows:
(1) Products with high appearance requirements, valuable instrument parts, and some painted parts with strict appearance requirements should be inspected one by one.
(2) For products in large quantities that require appearance quality classification, a general inspection should be carried out (100% of Lang for grading inspection).
(3) For products with large batches and unqualified appearance requirements, 5% to 10% of each batch of products can be selected for inspection. If any unqualified A certain number of unqualified products can be partially or completely returned for repair or reworked according to specific conditions .
In the visual inspection of the coating ●Surface defects are generally carried out by visual inspection. Roughness can be tested with special instruments. Although there are instruments to detect , it has not been widely used due to the influence of the shape of the coating and the color of the coating. At present, the visual method is still the main method. Coating coverage test is carried out by chemical method.