Coating may not be fully cured.
In this case the coating still contains solvents which allow the
path to earth to be formed even if a flaw is not present. To
overcome this problem, allow the coating to cure before
undertaking the test.
7.3.2 Concrete Substrates.
If concrete or cement contains sufficient moisture, then it will
conduct electricity and the holiday detector can be used to
detect flaws in its coating.
The test method is generally the same as before, but the
following points should be noted.
Check the suitability of the concrete for use with a holiday
detector as follows:-
- Make an earth contact by hammering a masonry nail or
similar into the concrete.
- Attach the earth lead to the nail and set test voltage for the
thickness of the coating, or in the range 3 - 6kV if a
specification for the test voltage is unknown.
- Place the probe on uncoated concrete about 4 metres (13
feet) from the nail.
- If the alarm sounds, then the concrete is sufficiently
conductive.
If the concrete is too dry to test, the alarm will not sound.
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