Definition - What does Holiday Test mean?
A holiday test is a non-destructive test method applied on protective coatings to detect unacceptable discontinuities such as pinholes and voids. Holiday testing involves checking an electric circuit to see if current flows to complete the circuit. This testing is used to find coating film discontinuities that are not readily visible.
A holiday test is usually performed on tank interiors, chemical storage vessels and buried structures because of the importance of maintaining adequate coating protection in aggressive service environments.
A holiday test is also known as a continuity test.
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Corrosionpedia explains Holiday Test
A holiday test is a non-destructive test carried out on a coating, such as a rubberized waterproofing coating on concrete, where holes through the coating are detected by the formation of an electrical circuit in areas where there is an insufficient coating to resist the electrical charge.
If an electrical flow is detected, then the test area is termed as conductive, indicating the presence of discontinuities such as pinholes and voids. A holiday test is commonly used in the offshore industries where piping and structures are coated with non-conductive coatings.
A holiday test is performed with a holiday detector, which is an electrical device used to determine the location of a gap or void in the coating. There are various techniques and tools available for holiday detection. Coatings applied to concrete substrates can also be tested for discontinuities using either a low-voltage or a high-voltage holiday detector, depending on the coating thickness.
A low-voltage holiday test is used when the coating system is less than 500 microns (20 mils) thick. A high-voltage holiday test is used when the coating system is thicker. High-voltage holiday testing requires special care not to damage the coating or cause injury to the operator.