This test method provides for easy detection of discontinuities and areas of light coverage that are not readily seen by visual inspection on corrosion protective porcelain enamel coatings. These two issues limit the protection to the metal substrate. Apparatus includes a nondestructive coating thickness gage, either an ac or a dc high-voltage discharge test instrument with a continuously variable output voltage, and a mesh wire gauze test probe. This test uses porcelain enameled glass coating specimens of any size which should be removed from an edge or the back of a specimen and then properly conditioned as specified. If the probe is wider than the specimen, the specimen edges should be masked using electrical insulating tape.

1.1 Porcelain enamel coatings are applied to metals to provide protection from corrosion as well as to enhance their appearance. This test method permits the easy detection of discontinuities and areas of light coverage, not readily seen by visual inspection, which limit the protection to the substrate. Somewhat similar tests applicable to the thicker glass coatings used for chemical reaction vessels are found in Test Methods C 536 and C 537.

1.2 Values stated in SI units are to be regarded as the standard. Inch-pound units are provided for information only.

1.3 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.