Characteristics: During the 180 degree test of steel bending, the coating of the machining parts is cracked and the coating is stripped.
1. The mastery of pretreatment is too much.
2. The thickness of coating is thicker.
3. Excessive baking.
4. The manufacturers of lower coating is different from the upper coating, or the use of paint thinner is improper.
2. Poor hardness (pencil hardness)
Characteristics: When marking on the surface of the coating emphatically with a drawing pencil, the surface will leave a scratch after wiping off .
1. The temperature of the furnace is low and the coating is not fully cured.
2. The heating condition is not appropriate.
3. The thickness of the coating is thicker than the specified thickness.
3. Salient point
Characteristics: Due to the external clash of the steel strip, the surface of the plate appears to be prominent or sunked.
Some salient points have a certain distance and some salient points does not have.
1. The rolls are mixed with foreign objects when it is painted.
2. The sheet products have a ligation when they are tied.
3. It is subjected to external shocks when reeling.
4. Edge bubble
Characteristics: Both sides are coated with paint and after drying, the bubbles appear.
Causes:The raw material has burrs and paint. Besides, there is a crack on both sides.
5. Pocking mark
Characteristics: There are protuding like grains on some or all of the surface after the application with the foreign objects or dust.
1. Paint is mixed with other kinds of coatings or other companies' coating.
2. There is a mixture of foreign objects in the paint.
3. In the process of pretreatment, there is a poor washing.
6. Orange peel
Characteristics: The dry surface coating is rough and uneven as orange peel.
1. The wet film is too thick.
2. The viscosity of the coating is high.
7. Poor solvent resistance (MEK)
Characteristics: There is a punctate paint after wiping with butanone.
1. The baking temperature did not meet the requirements.
2. There is a problem in the curing of the coatings.
3. The pretreatment is not clean.
8. Unqualified clash
Characteristics: The paint with the adhesive tape is partially or completely peeled after clash.
1. The preprocessing is not good.
2. Check whether the curing temperature of the paint is reasonable.
9. Shrinkage cavity
Characteristics: The lacquer film is not smooth and some local surface comes out.
1. The surface of the steel strip is unclean.
2. The cooling water of the primer is unclean.
3. The viscosity of the coating did not meet the requirements of the machine.