Grinning

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Definition - What does Grinning mean?

Grinning is a coating defect where a material's underlying surface is observable through the paint due to an inadequate coating of paint on the material, insufficient hiding power, or when air bubbles that formed on the paint's surface have burst.

An inadequate coating application can be harmful because the material is open to harsh environments and corrosion can form on the surface.

Grinning may also be known as grinning through or incomplete hiding.

Corrosionpedia explains Grinning

In the grinning process, the material's surface that was coated with a paint film or coating is still visible. This happens when the coating or paint has an inadequate hiding capacity due to an ineffective application or the formation of bubbles between coating layers and the bubbles have burst, exposing the inner surface to the atmosphere.

The probable causes of grinning are:

  • The coating layer is too thin on the surface of the material.
  • Volume of coating used is low (attempting to cover the area with an insufficient amount of coating).
  • Poor opacity and low covering power of the top coat.
  • The use of a strong color for the primer or undercoats.
  • Low experience in applying coatings.

The grinning process can be prevented by:

  • Applying an adequate amount of coating between individual coats of the primer and color.
  • Using coatings with good opacity.
If grinning is observed, it can be repaired by applying another compatible coat to the grinned area.

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