What are the reasons for poor powder curing in powder coating application

Update:12-12-2020
Summary:

The reasons why the powder coating process affects the […]

The reasons why the powder coating process affects the poor curing of the coating are as follows:

The baking temperature of the baking oven fails to reach the baking temperature required by the powder coating

Although the control temperature of the baking oven can easily reach the design temperature or the baking temperature required by the powder coating when there is no load, under full load, due to insufficient total heat supply, sometimes it may not reach the design temperature or the powder coating temperature. The baking temperature required, especially in the winter workshop in northern areas, is low. If the heat preservation condition of the baking furnace is poor, the temperature of the coating is low before entering the baking furnace, and the coating material has a thick wall and large heat capacity, it is easier This problem occurs.

When the temperature of the baking oven cannot reach the curing temperature of the powder coating, the problem of temperature compliance can be solved by increasing the heating power; in addition, the curing purpose can also be achieved by extending the curing time
In the baking oven, the baking curing time did not reach the baking time required by the powder coating

In the baking conditions of powder coatings, the baking time refers to the baking time calculated after the coated object reaches the baking temperature, rather than the time calculated after the coated object is placed in the baking oven.

When the material to be coated is thicker and more pieces are hung, the heat capacity of the object is larger, and the time it takes for the object to heat up to the controlled temperature is longer. In a certain length of baking oven, when the speed of the conveyor chain does not change, the effective baking time is shorter. If the effective baking time is not enough, the coating film will not be cured completely, and the physical and mechanical properties of the coating film will not meet the requirements.

Therefore, in powder coating, it is best to use the furnace temperature tracking tester to measure the temperature change of the coated object in the baking furnace under full load conditions to determine a reasonable baking curing temperature and time, so as to ensure the coating film It is completely cured, while also ensuring the physical and mechanical properties of the coating film.
The surface of the coated object is not treated well

If the oil on the surface of the coated object is not cleaned, the oxide scale or rust is not removed, or the quality of the phosphating film is not good, a lot of phosphating liquid residue is stained on the surface, etc., the adhesion of the coating film and the substrate after powder coating It will also lead to poor impact resistance of the coating film. This situation must be solved by improving the surface treatment quality of the coated object.
In terms of coating film performance inspection, it should be carried out in strict accordance with the test temperature and film thickness specified in the product standard

Generally speaking, the thickness of the coating film is thicker than specified; when the temperature in the laboratory is lower than the specified temperature, the coating film has poor impact resistance, flexibility, cupping test and adhesion properties, and it is not easy to pass;

When the coating film thickness is thin and the test temperature is higher than the specified temperature, these physical and mechanical properties can be easily passed. From the perspective of ensuring product quality, try to test the performance indicators of the coating film under relatively harsh conditions to ensure the quality of the coating product without fail.

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