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 coating of at least 150 mm thickness (see Note) on a conductive substrate, using the high voltage or ‘brush’ method.NOTE: Where coatings are less than 150 mm thick, an alternative method such as the low voltage wet sponge method should be used.This Standard is applicable to site testing of coated metal items of equipment or structures which may be subjected to long-term burial or immersion, such as structural steel, pipelines, storage vessels, bridges and mobile/transportable containers. The method is confined to testing instruments that can provide a minimum voltage of 500 V. 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 voltages recommended in this Standard are intended to be applied under conditions of normal atmospheric pressure and temperature.