Definition - What does Checking mean?
Checking is a visible coating defect that occurs due to improper coating application on a metal surface with the intention of preventing corrosion. It is characterized by minute fine cracks on the surface of an applied topcoat. The presence of checking can leave a metal object's surface vulnerable to corrosion.
Corrosionpedia explains Checking
Checking typically occurs due to the formation of stresses along a paint film surface, causing it to become brittle and prone to fractures.
Checking may be prevented by carefully evaluating the chemical composition of all paint components and understanding how they react to a given fixed curing temperature. An occurrence of checking may be repaired by thoroughly cleaning the substrate's surface before applying a topcoat or undercoat.