AS 3894.2-1991

Sets out a method of determining the presence of pinholes, holidays, cracks, and other discontinuities in non-conductive coatings of thickness less than 250 micrometres, using the wet sponge method with an extra-low-voltage testing instrument.

This Standard sets out a test method for determining the presence of pinholes, holidays, cracks and other discontinuities which penetrate to the substrate in a non-conductive, protective thin film coating of less than 250 mm thickness, or where metal particles protrude through the coating (see Note 1).This Standard is applicable to coated metal items, equipment or structures that may be subjected to long-term burial or immersion, are in continuous contact with a moist, chemically aggressive environment, and require a greater degree of protection than is normally necessary for items exposed to the atmosphere. Examples of such items include structural steel, pipelines, storage vessels, bridges and mobile/transportable containers. The Standard is not intended to apply to coating types incorporating components which conduct an electric current, such as zinc dust and aluminium flakes. The method is confined to measuring instruments that provide a maximum voltage of 90 V d.c.Although it may be used in the laboratory for inspecting panels and relatively small test items, the method is intended for use in the field (see also Clause 9).This test will not detect areas of low film thickness or inclusions in the coating.NOTES:1 Where coatings are greater than 150 mm thick, an alternative method such as the high voltage (brush) method may be used.2 This test is not recommended for use on intermediate coats of a multicoat system, as intercoat adhesion may be affected.

First published as AS 3894.2-1991.