News - I met many problems during powder spraying, how to solve them?

I met many problems during powder spraying, how to solve them

1. Coating impurities

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

1) Solidify impurities in the furnace. The solution is to thoroughly clean the inner wall of the curing furnace with a wet cloth and a vacuum cleaner, focusing on the gap between the suspension chain and the air duct. If it is a large black particle impurity, it is necessary to check whether the filter screen of the air supply pipe is damaged, and replace it in time.

2) Impurities in the powder spraying room. It is mainly dust, clothing fiber, equipment abrasive particles and dust deposit of powder spraying system. The solution is to use compressed air to purge the dusting system before starting work every day, and thoroughly clean the dusting equipment and dusting room with wet cloth and vacuum cleaner.

3) Hanging chain impurities. It is mainly the product of corrosion of hanging chain oil baffle and primary hanger water tray (made of hot-dip galvanized sheet) by pretreatment acid and alkali vapor. The solution is to clean these facilities regularly.

4) Powder impurities. It is mainly caused by excessive powder additives, uneven pigment dispersion, and powder spots caused by powder extrusion. The solution is to improve the quality of powder and improve the way of powder storage and transportation.

5) Pre treatment impurities. It is mainly the large particle impurities caused by phosphating slag and the flakes of small impurities caused by yellow rust of phosphating film. The solution is to timely clean up the slags in the phosphating tank and spraying pipeline, and control the concentration and proportion of phosphating tank liquid.

6) Impurities in water quality. It is mainly the impurities caused by excessive sand content and salt content in the water used for pretreatment. The solution is to add a water filter and use pure water as the last two stages of cleaning water.

2. Coating shrinkage cavity

1) Shrinkage caused by residue of surfactant due to unclean oil removal of pretreatment or unclean water washing after oil removal. The solution is to control the concentration and proportion of pre degreasing tank and degreasing tank liquid, reduce the amount of oil in the workpiece and strengthen the water washing effect.

2) Shrinkage caused by excessive oil content in water. The solution is to add water inlet filter to prevent oil leakage of water supply pump.

3) Shrinkage caused by excessive water content of compressed air. The solution is to discharge the condensed water of compressed air in time.

4) Shrinkage caused by moisture in powder. The solution is to improve the storage and transportation conditions of powder and add dehumidifiers to ensure the timely use of recycled powder.

5) Shrinkage caused by oil dirt on the suspension chain falling onto the workpiece by the air conditioner. The solution is to change the position and direction of the air supply outlet of the air conditioner.

6) Shrinkage caused by mixing powder. The solution is to thoroughly clean the powder spraying system when changing powder.

3. Color difference of coating

1) Color difference caused by uneven distribution of powder pigments. The solution is to improve the quality of the powder and ensure that L, a and b of the powder have little difference and the positive and negative are uniform.

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

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 operates well to ensure uniform coating thickness

3. Poor adhesion of coating

1) Poor adhesion caused by residual degreaser, chromizing slag on the workpiece or the water washing tank polluted by alkali liquor due to incomplete water washing of pretreatment. The solution is to strengthen water washing, adjust the degreasing process parameters and prevent the degreasing solution from entering the water washing tank after phosphating

2) Poor adhesion caused by yellowing and blooming of phosphating film or no phosphating film locally. The solution is to adjust the concentration and proportion of phosphating bath solution and increase the phosphating temperature.

3) Poor adhesion caused by the unclean moisture in the corners of the workpiece. The solution is to increase the drying temperature.

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

5) The adhesion of deep well water is poor due to excessive oil and salt content. The solution is to add an inlet filter and use pure water as the last two cleaning water. In a word, there are many electrostatic powder spraying technologies and their application methods, which need to be flexibly applied in practice

4.Color difference of coating

1) Color difference caused by uneven distribution of powder pigments. The solution is to improve the quality of the powder and ensure that L, a and b of the powder have little difference and the positive and negative are uniform.

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

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 operates well to ensure uniform coating thickness

5. Powder coated orange peel

1) Judgment method for orange peel appearance of powder coating:

(1) Visual method

In this test, the sample plate is placed under a double tube fluorescent lamp. The reflective light source of the template can be obtained by placing the template appropriately. Qualitative analysis of the clarity of reflected light can visually assess the flow and leveling properties. In the case of poor fluidity (orange peel), the two fluorescent tubes look vague and unclear, while the products with high fluidity can obtain clear reflection.

(2) "Profile measurement method"

In this method, the surface shape is recorded by the offset of the highly sensitive probe. Thus, roughness, orange peel and poor flow caused by shrinkage cavity, pinhole or dirt can be quickly distinguished.

2) Avoid orange peel

In the new equipment manufacturing coating, the coating appearance becomes more and more important. Therefore, one of the main goals of the coating industry is to achieve the best coating performance according to the final requirements of users, which also includes the satisfaction of the surface appearance. The surface condition affects the visual effect through such factors as color, luster, haze and surface structure. Gloss and image clarity are often used to control the appearance of coatings. However, even if a film with high glossiness is used, its surface fluctuation also affects the appearance of the whole film. At the same time, it is believed that the gloss measurement cannot control the visual effect of fluctuation, which is also called "orange peel". Orange peel or microwave is a wavy structure with the size between 0.1mm and 10mm. On the high gloss coating surface, people can see wavy, bright and dark areas.

It should be pointed out that sometimes a certain degree of fluctuation or ripple structure is purposefully designed to cover the surface defects of the substrate or obtain a special coating surface appearance