AS 3894.1:2002 pdf – Site testing of protective coatings Method 1: Non-conductive coatings- – Continuity testing- High voltage (‘brush’) method .
6 MATERIALS
6.1 Cleaning solutions/agents
Alkaline oil emulsifiers in solution, or solvent recommended for this purpose by the manufacturer of the coating.
For routine testing, potable water shall be used throughout the test (e.g. for preparing solutions or rinsing operations). The water shall be free of any levels of impurities that would affect the outcome of the test.
For referee testing, the water shall have a conductivity 50 jiS.
6.2 Marker
A suitable marker, such as chalk or a spirit pen, used to mark the position of defects. Crayon or grease-based materials shall not be used.
7 APPARATUS
7.1 High voltage tester
7.1.1 General
The high voltage test unit shall be of robust construction. The essential components of the high voltage tester shall comply with the requirements of Clauses 7.1.2 to 7.1.7.
The high voltage tester shall be calibrated in accordance with Appendix B.
NOTE: Guidance on checking high voltage testers is given in Appendix C. 7. 1 .2 Power s upplv
The power supply shall deliver d.c. voltage, either continuous or pulsed, suitable for the coating to be tested, which may be adjusted in increments as described in Clause 7.1.4(c), and is stable to within ±2% at the power output points and display meter for the duration of the test. The output voltage shall be measured under load conditions.
If the source of power is a battery and there is doubt about battery condition, a fully charged battery should be installed prior to commencing the test.
7.1.3 Detector
The detector unit is usually located in a common housing with the power supply (see Clause 7. 1 .2), and is designed to indicate the flow of current, in the form of a spark passing from the electrode to the substrate, through a defect (pinhole, holiday or reduced film thickness) in the coating on the test item. The detector exhibits the current flow visually or audibly by means of a pointer, a spark, a light-emitting diode (LED) or a loudspeaker (which may be in the form of a headphone). To avoid false indications, the sensitivity of the alarm may be altered to allow use on coatings of various generic types and under differing test conditions.
7.1 .5 Indicators
The combined unit described in Clauses 7.1.2 and 7.1.3 shall have the following additional features:
(a) Voltage indicator A visual display that indicates the nominal voltage at the probe tip relative to ground, accurate to within ±5% of the true value. The detector shall be fitted with a visual display indicating the nominal voltage at the probe tip relative to the ground, to the nearest 10 V.
(b) Batten’ condition indicator Battery-operated detector fitted with a visual or audible transducer that indicates the suitability or condition of the battery for subsequent use.
(c) AIar,n-discontinuit’,’ indicator A visual and audible alarm system to indicate the presence of the defect in the test coating. The sensitivity of the alarm should be adjustable and a visible indicator may be fitted.
7.1.6 Electrodes
For routine purposes, and depending upon the item to be tested, the electrode or probe shall
be in the form of one of the following:
(a) Brush-type electrode Consisting of a continuous, multi-stranded linear brush (see Note) of design such that, when passed over the test surface in the recommended manner, the bristle density and the stiffness of the fibre will ensure that the electrode provides an unbroken sweep over the test area, that is, all points of the surface in the path of the brush will be electrically swept.
AS 3894.1:2002 pdf – Site testing of protective coatings Method 1: Non-conductive coatings- – Continuity testing- High voltage (‘brush’) method .
