Recording penetrative defects in glass enamel coatings

When checking the continuity and integrity of protective enamel coatings, the simplest method of detecting faults is by the use of a high-voltage spark discharge. However, the spark method does not provide information on the form, number and distribution of such faults over the surface. The defectiveness of enamel coatings was determined using a corona-discharge method. The use of a corona discharge instead of a spark makes it easy to record the presence of defects, their number in a given area, the arrangement, and also their type. Gaseous inclusions in the form of bubbles were commonly found. Electrolytic gas separation can be used independently or in combination with the corona discharge to register the defects and to determine their number and distribution.