Definition - What does Grinning mean?

Grinning, also called “grinning through,” is the underlying surface on a material that is visible through the paint film because of an inadequate coating of paint on the material, which thereby has inadequate hiding power. Inadequate application of coating material can be harmful to the material because it is open to harsh environments and can form corrosion on the surface.

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Corrosionpedia explains Grinning

In the grinning process, the underlying surface of the material is visible through the paint film due to the inadequate hiding power of the coating material. It is often seen where dark colors are coated with lighter colors.

The probable causes of grinning are:

  • Low film thickness of the penultimate coat on the surface of the material.
  • Poor opacity and low covering power of the top coat on the corrosive material surface.
  • The use of a strong color for the primer or undercoats.

The grinning process can be prevented by following the below procedures:

  • Applying adequate dry film thickness between individual coats of the primer and color.
  • Using opaque coatings with good opacity.
If grinning is observed on any material, it can be repaired by applying additional compatible coats to the grinned area and a clean surface.

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