Understanding of shrinkage cavity of coating equipment and coating products

1: The leveling agent or defoamer of the coating itself is too small or unevenly dispersed, resulting in the absence of leveling agent or defoamer in the powder particles of the surface workpiece during spraying.

2: because the cleaning of coating equipment is not clean, the coating process is uneven or impurity.

3: When using compressed air, oil and moisture are brought into the paint spraying.

4: On the surface of coated products, when the oil removal process before coating is not clean, there is oil stain on the coated object with rough surface or pinholes. After phosphating, the oil stain still remains on the coated object, and the formed coating is easy to produce shrinkage pores.

5: The surface of coating products is uneven, especially the surface of coated objects such as cast iron, aluminum and hot-rolled steel plate is uneven, and there are pores. During the coating process, when the coating melts and flows, the air in the pores will expand by heating, and the solidified coating film will bulge out. If the coating film cannot be leveled, shrinkage pores will be formed.

6: The residual water on the surface of the coated object after product surface treatment. When the coated object with residual water is baked after coating, the water volatilization will cause shrinkage of the coating film.