What are the reasons for Pre Painted Galvanized Steel Sheet quality problems? Share it with everyone; I hope it helps.
1. Characteristics of poor bending of color steel coils (T-bend): When the steel is bent 180 degrees in the test, the coating of the processed part will crack and peel off.
Cause: The amount of pre-processing is too much. The coating thickness is too thick. Overbaked. The lower coating is made by a different manufacturer than the upper coating, or the thinner is used improperly.
2. Characteristics of the poor hardness of color steel coils (pencil hardness): use a drawing pencil to draw a line on the surface of the coating, and wipe it off leaving a scratch on the surface.
Cause: The furnace temperature is low, and the coating is not sufficiently cured. Inappropriate heating conditions. The coating thickness is thicker than specified.
3. Colored steel coils have the characteristics of convex points: due to external impact on the steel strip, protrusions or depressions appear on the surface of the plate, some with a certain spacing, and some without.
Cause: Foreign matter was mixed on the roller during painting. Puncture marks when bundling thin plate products. Received external impact when rewinding.
4. The color steel curling part has bubbles: there is paint on both sides, and after drying, bubbles appear.
Cause: The raw material has burrs, is stained with paint, and has gaps on both sides.
5. Characteristics of pitting on color steel coils: Foreign matter or dust mixed in from the outside will appear like rice grains protruding on part or all of the surface after painting.
Cause: The paint is mixed with other types of paints from other companies. Caused by foreign matter mixed in the paint. Poor washing during pre-treatment.
6. Characteristics of orange peel on color steel coils: The dried surface coating is as rough and uneven as orange peel.
Cause: The wet film is too thick. When the viscosity of the paint is high.