Common problems and solutions in electrostatic powder coating operations

1 Coating impurities 

Common impurities mainly come from particles in the powder spraying environment and impurities caused by various other factors, which are summarized as follows

1.

1.

1.

1.

1.

1.

2 Coating shrinkage

2.

2.

2.

2.

2.

2.

3 Coating color difference

3.

3.
2 Color difference caused by different curing temperatures
.
The solution is to control the set temperature and conveyor chain speed to maintain the consistency and stability of the workpiece curing temperature and time
.

3.
3 Color difference caused by uneven coating thickness
.
The solution is to adjust the powder spraying process parameters and ensure that the powder spraying equipment runs well to ensure uniform coating thickness

4 Poor coating adhesion

4.
1 Incomplete pre-treatment water washing results in poor adhesion caused by residual degreasing agent, chromium residue on the workpiece, or the washing tank is polluted by lye
.
The solution is to strengthen the water washing, adjust the degreasing process parameters and prevent the degreasing liquid from entering the washing tank after phosphating
.

4.
2 The adhesion of the phosphate coating is poor due to yellowing, blooming or partial absence of the phosphate coating
.
The solution is to adjust the concentration and ratio of the phosphating bath solution and increase the phosphating temperature
.

4.
3 Poor adhesion caused by poor moisture drying at the corners of the workpiece
.
The solution is to increase the drying temperature

4.
4 Insufficient curing temperature causes poor adhesion on a large area of ​​the coating
.
The solution is to increase the curing temperature

4.
5 Poor adhesion caused by excessive oil content and salt content in deep well water
.
The solution is to add a water inlet filter and use pure water as the last two cleaning water
.
In short, there are still many powder electrostatic spraying technologies and their application methods, which need to be used flexibly in practice
.

5 powder-coated orange peel

5.
1 Judgment method of powder coating orange peel appearance:

(1) Visual inspection

In this test, the prototype is placed under a double-tube fluorescent lamp
.
The reflected light source of the template can be obtained by properly placing the template
.
Qualitative analysis of the clarity of the reflected light can visually evaluate the flow and leveling properties
.
In the case of poor fluidity (orange peel), the two fluorescent tubes look fuzzy and unclear, while high fluidity products can obtain clear reflections
.

(2) "Shape measurement method"

In this method, the surface shape is recorded by the offset of the highly sensitive probe
.
This can quickly distinguish roughness, orange peel and poor flow caused by shrinkage, pinholes or dirt

5.
2 Avoid the occurrence of orange peel 

In the coating of new equipment manufacturing, the appearance of the coating becomes more and more important
.
Therefore, one of the main goals of the coatings industry is to optimize the performance of the coatings according to the final requirements of users, which also includes satisfactory surface appearance
.
The surface condition affects the visual effect through factors such as color, gloss, haze and surface structure
.
Gloss and image clarity are often used to control the appearance of the coating
.
However, even if the coating film with high gloss is used, the fluctuation of the surface also affects the appearance of the entire coating film.
At the same time, it is believed that the gloss measurement can not control the visual effect of fluctuation.
This effect is also called "orange peel"
.

Orange peel or micro wave is a corrugated structure with a size between 0.
1mm and 10mm
.
On the high-gloss coating surface, people can see wavy, light and dark areas
.
Two different levels of fluctuations can be distinguished: long fluctuations, also called orange peels, which are the fluctuations that can be observed at an interval of 2 to 3 distances; the other is called short fluctuations or micro fluctuations, which are observed at a distance of about 50 cm To the volatility
.

It should be pointed out that sometimes in order to cover the surface defects of the substrate or obtain a special coating surface appearance, a certain degree of undulation or ripple structure is purposely designed
.

Therefore, "orange peel" can be defined as the "wavy structure of a high-gloss surface", which gives the surface of the paint layer a streaked, unleveled visual appearance
.