7. Coating Failures

7.4 Types of Failures

(C) Alligatoring


Very large checks several inches across, visible to the eye are formed. The large checks resemble the skin of alligators, hence the name "alligatoring".





This defect is very common amongst coal tar coatings. If a thick coal tar coating is applied, there is a tendency for the outer surface area of the coating to shrink at a faster rate than the body of the coating, resulting in formation of macro checks which cause the coating to become brittle. The macrochecks maintain a minimum thickness so that the damage does not penetrate into the substrate.



  • Avoid applying a soft primer under a hardcoat.

  • do not apply a coating which has a tendency to oxidize on a soft surface.

  • Use reinforcing pigments.

  • Monitor the coatings periodically.