What does a "holiday" refer to in coating terminology?

In coating terminology, a "holiday" specifically refers to an area where the protective coating is missing, resulting in exposed substrate. This can occur in conductive coatings where a gap or defect allows the underlying surface, such as metal or concrete, to be exposed to the environment. These areas are problematic as they make the substrate susceptible to corrosion, oxidation, and other forms of degradation, which can compromise the integrity and lifespan of the underlying material.

Recognizing holidays is essential for quality control in coating applications since they can lead to significant failures in a protective system. Proper coating inspection involves checking for such defects, ensuring the coating is continuous and provides the intended protection. Understanding the concept of a holiday is crucial for coatings inspectors, as it informs them of the critical need to achieve uniform application and thorough coverage when applying protective coatings.