The gloss of the paint film is reflected by its ability to reflect light, which is the key factor to judge the appearance quality of the paint film. When the surface of the paint film is rough, the light is easy to diffuse, resulting in low gloss; With a smooth surface, the light can be reflected in one direction and the brightness intensity is high, and the gloss is high. The intensity of the reflected light depends not only on the smoothness of the surface of the paint film, but also on the amount of reflection and transmission of the projected light by the paint film.
A common situation where the body paint film needs to be repaired
Passenger car body paint film is prone to a variety of problems. Blurry and dark, or due to humidity and coating problems, it can be cured and polished, and it needs to be smoothed and sprayed again; Stains and water stains, from ventilation and compressed air, can be cleaned and polished, heavy need to be polished and sprayed; Wrinkles are caused by solvent volatilization, spraying and drying, and the process needs to be adjusted. Glossy color and coverage problems, due to the wrong paint composition and spraying parameters, it is necessary to select the paint adjustment parameters, re-evaluate the process and repair or re-spray; Infiltration is the bottom paint film or old paint improper treatment, to polish and clean the old paint film, choose impermeable coating, has penetrated need to be thoroughly resprayed; Due to the poor spraying technology, the flow mark should be trained to standardize the operation, and it can be resprayed or re-sprayed after grinding; The pits and orange peel are caused by the problems of coating, environment and Spray Gun, and it is necessary to choose a good paint control environment adjustment Spray Gun, which can be sanded and repaired or resprayed; Due to the problem of metal surface treatment and primer topcoat matching, delamination should be pretreated and selected with paint, and the delamination needs to be removed and resprayed; Cracks are caused by shrinkage stress and use environment, and the drying speed should be controlled to maintain flexibility. Due to the grinding process, the sand mark should be optimized to select sandpaper, which can be finely ground and polished. Due to the difference between the repair connection and the coating, the connection should be treated and the matching paint should be selected, and the paint needs to be reprocessed; Due to the air and humid environment of the coating, the bubble blister should be stirred and degassed to control the pressure to keep it dry, and it has been repaired or resprayed according to the severity; Lack of paint is due to the problem of Spray Gun or spraying path, to check the Spray Gun optimization path, the missing part needs to be sprayed.
Method for detecting the gloss of body paint film
Visual method - evaluation by direct observation of the reflected light from the surface of the paint film by the human eye under a specific light source and viewing angle. However, this method is greatly affected by the subjective factors of the observer, and different people may judge the gloss differently, and the accuracy and reliability of the evaluation results are relatively low.
Contrast method - compare the paint film to be tested with a standard sample with a known accurate gloss value to determine the gloss difference. However, this method is also subjective, and has high requirements for the preservation and use of standard templates, and the aging and wear of the samples may affect the comparison results.
Instrumentation – Measurement with a specialized gloss meter, which is currently the most widely used and accurate method. The gloss meter can simulate the observation conditions of the human eye and quantitatively evaluate the reflected light on the surface of the paint film. The intensity of reflected light is usually measured by irradiating the paint film at an angle of incidence of 60°, and different angles (such as 20°, 45°, 85°, etc.) can reflect the different characteristics of the paint film. The instrument is irradiated by light sources such as incandescent lamps, halogen lamps or LEDs, and uses sensors such as photodiodes and photomultiplier tubes to receive the reflected light and convert it into electrical signals.
summary
This article focuses on the paint film of passenger car body, and describes in detail the gloss of the paint film, common problems that need to be repaired and detection methods. The gloss of the paint film is the key to judge the appearance quality of the paint film, which is affected by the smoothness of the paint film surface and the reflection and transmittance of light. There are various common problems of body paint film, and the causes involve many aspects such as environment, coating, process, and operation, and the repair methods vary according to the severity and cause of the problem. Among the detection methods, the visual method relies on human observation and is highly subjective. The comparison method is compared with the standard model, but the requirements for the model are high and subjective; With the help of gloss meter, the instrument method is irradiated by a light source at a specific angle, and realizes objective, accurate and repeatable quantitative evaluation through sensor and series treatment, which is widely used and plays an important role in the quality control of body coating.
