Powder coating is a solid powder synthetic resin coating composed of solid resin, pigments, fillers, and additives. At room temperature, it is stored stably and then subjected to electrostatic spraying, friction spraying (thermosetting method), or fluidized bed immersion coating (thermoplastic method), followed by heating, baking, melting, and solidification to form a smooth and shiny permanent coating film, achieving the purpose of decoration and corrosion prevention. Common anti-corrosion powder coatings are divided into ordinary modified anti-corrosion coatings, fusion bonded epoxy powder coatings, and epoxy zinc rich powder coatings. After powder coating, the coating should be evaluated from the following perspectives to determine whether it meets the requirements.

1、 Appearance inspection. Under natural light, when inspecting workpieces from different angles, it is required that the paint film on the entire workpiece must be flat, without obvious particles, stains, water bubbles, and pits, otherwise it will rust over time; It can be seen that there is no accumulation of powder on the surface; There should be no obvious orange lines, and pure color coatings should not have any mixed colors; There should be no phenomenon of exposing the base due to insufficient powder content.

2、 Film thickness. Using a magnetic thickness gauge with an accuracy of 2um, measuring at least three positions with a thickness of 80-120um.

3、 Hardness. Use a hardness tester and draw a line with a 1H pencil to check for dents. If there are no dents, it is considered qualified. The hardness of the coating is related to the degree of curing and powder coating. The hardness of the coating is usually around 1H-3H, and some coatings with special requirements can achieve 3H-8H. The hardness of common indoor powders is lower than that of outdoor powders, and hardness testing pens are generally used for testing.

4、 Adhesion. The pre-treatment of the workpiece, the roughness of the workpiece itself, the roughness of the workpiece surface, the degree of curing, powder coating, etc. are all related to adhesion. You can use a blade to mark the grid or a white grid knife to test, which meets the requirements of 0‐ The qualification standard for Level 1. Level 0: The cutting edge is completely smooth without any detachment; Level 1: There is a slight coating peeling off at the intersection of the incision, but the affected cross cutting area cannot be significantly greater than 5%.

5、 Impact resistance. Conduct 3 impact tests using an impact tester to check for cracks. If there are no cracks, it is considered qualified (50cm. Kg, punch ball diameter 20mm).

6、 Glossiness. A 60 degree mirror reflectivity greater than 75% is considered qualified.

7、 Weather resistance. Aging machines and salt spray testing machines can be used to test the UV resistance and thermal performance of coatings. The aging machine tests the coating's resistance to ultraviolet radiation and temperature, and the weather resistance of the coating is tested by the discoloration of the coating. An artificial accelerated aging test is conducted for 500 hours, and a comprehensive evaluation is conducted; Level 1 is considered qualified. Outdoor powder generally has better weather resistance than indoor powder. The salt spray testing machine is used to test the corrosion resistance of coatings, and the testing time is used to determine the quality of coating performance.

8、 Powder rate. The powder coating coverage rate of powder coating generally refers to the coverage rate of powder spraying. The most critical issue while ensuring the appearance and mechanical properties of the powder coating is the amount of powder coating consumed per unit profile, which is the production cost. Therefore, the powder coating rate is a very important factor.

The environmental friendliness of coatings is directly related to their VOC content, and low VOC coatings have become a trendsetter in the coatings industry. Powder coating, as a 100% solid coating that does not contain any VOCs, is becoming a darling of the market and a modern new type of coating product. If there is excessive or overspray, a recycling system can be used to recover and reuse the excess paint, reducing environmental pollution. It has the characteristics of no solvents, no pollution, energy conservation, reduced labor intensity, and high mechanical strength of the coating.