Analysis of Quality Issues of Color Steel Plate Manufacturers
Add time：
2015-05-08
I. Poor Bending Property (T-bend)
Characteristics:
When the steel is bent 180 degrees, the coating at the processed area cracks and peels off.
Causes:
1. Excessive pretreatment.
2. Coating thickness is too thick.
3. Excessive baking.
4. The base coat and top coat are from different manufacturers, or improper thinner is used.
II. Poor Hardness (Pencil Hardness)
Characteristics:
Draw a line on the coating surface with a drafting pencil; after wiping it off, a scratch remains on the surface.
Causes:
1. Low furnace temperature; the coating is not fully cured.
2. Inappropriate heating conditions.
3. The coating thickness exceeds the specified thickness.
III. Bumps
Characteristics:
Due to external impact on the steel strip, protrusions or indentations appear on the surface of the plate; some have a certain spacing, while others do not.
Causes:
1. Foreign matter is mixed into the roller during coating.
2. Binding marks on the thin plate products during bundling.
3. External impact during rewinding.
IV. Edge Bubbles
Characteristics:
Both sides have coatings; after drying, bubbles appear.
Causes:
The raw material has burrs and excessive coating on both sides, resulting in gaps.
V. Pinholes
Characteristics:
Foreign objects or dust mixed from the outside; after coating, some or all surfaces have rice-grain-like protrusions.
Causes:
1. Other types or other companies' coatings are mixed into the coating.
2. Foreign objects are mixed into the coating.
3. Poor washing during pretreatment.
VI. Orange Peel
Characteristics:
The dried surface coating is rough and uneven, similar to orange peel.
Causes:
1. Wet film is too thick.
2. When the coating viscosity is high.
VII. Poor Solvent Resistance (MEK)
Characteristics:
Spot-like paint peeling after wiping with methyl ethyl ketone.
Causes:
1. Baking temperature does not meet requirements.
2. There is a problem with the curing of the coating.
3. The pretreatment cleaning is not thorough.
VIII. Impact Failure
Characteristics:
After the film is impacted and taped, some or all of the paint peels off.
Causes:
1. Poor pretreatment.
2. Check if the topcoat curing temperature is reasonable.
IX. Pinholing
Characteristics:
Uneven coating, local exposure of the substrate.
Causes:
1. The steel strip surface is unclean.
2. The base coat cooling water is unclean.
3. The coating viscosity does not meet the requirements for machine application.
X. Coating Missing
Characteristics:
Topcoat is not applied.
Causes:
1. Topcoat is not applied at the edges; poor substrate shape or insufficient pressure between the coating roller and back roller.
2. Topcoat is not applied in the middle of the plate; water or other foreign matter on the plate surface after base coat cooling.
XI. Color Difference
Characteristics:
Color difference from the standard plate.
Causes:
1. Coating thickness is too thick or too thin.
2. Not the same batch of coating.
3. Uneven stirring during viscosity dilution.
XII. Poor Gloss
Characteristics:
Abnormal gloss range.
Causes:
1. Inappropriate coating thickness.
2. Inappropriate curing conditions.
3. Insufficient stirring.
XIII. Coil Collapse
Characteristics:
Inner diameter deformation of the steel coil after winding and storage.
Causes:
1. The steel coil is affected by external forces after winding.
2. Incorrect winding tension.
3. Uneven load.
XIV. Sticking
Characteristics:
Slight peeling during unwinding; base coat sticking back will produce millet-like particles; uneven surface after applying topcoat.
Causes:
1. Insufficient cooling before winding.
2. Insufficient baking.
3. Some loads are too heavy.
XV. Pressure Damage
Characteristics:
Pitting after coating.
Causes:
1. Pressure damage on raw material coils.
2. Pressure damage caused by various rollers before coating.
3. Scratches after coating and together with the coating.
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