Chapter 10: Common Coating Defects and Solutions

Identifying Defects

• Chatter: From vibrations or flow fluctuations; exacerbated by high speed or mismatched viscosity.

• Ribbing: Bead instability; common in low viscosity at high gaps.

• Air Entrainment/Entrapment: Air in fluid; worse with high speed or porous substrates.

• Dewetting: Tension gradients; affected by substrate energy and temperature.

• Streaks/Particles: Contaminants; particle size > gap/10 causes this.

• Chevrons/Hashmarks: Acoustic or gravity issues; influenced by solids % and flow.

• Uneven Thickness: Misalignment; width and speed amplify.

• Edge Build-Up: Overflow; poor manifold for wide coatings.

Prevention Strategies

Adjust parameters like temperature to control viscosity; filter for particles. Regular maintenance and process modeling, per Coating Tech resources, prevent most issues.

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