This Standard provides a practical test method for the on-site determination of the presence of pinholes, holidays, cracks and other discontinuities that 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 test will not detect areas of low film thickness or inclusions in the coating. For a test method that accurately detects areas of low film thickness or inclusions, see AS/NZS 3894.1.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 that 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).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.
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