Elcometer 266 Manual Del Usuario página 25

14 SPECIAL CONSIDERATIONS (continued)
Surface moisture or contamination: Certain soluble salts

attract moisture from the atmosphere and this and other forms of
surface contamination can form a path across the surface to the
high voltage that is not due to a coating flaw. Under these
conditions the detector indicates non-existent flaws. When these
circumstances occur, the surface should either be dried using a
suitable cloth or cleaned with a non-conducting cleaner or solvent
which will not damage the coating.
Note: Ensure that any cleaner or solvent containers are removed from the test
area before re-commencing the test.
Moisture penetration or absorption: Moisture can enter

materials, e.g. glass reinforced plastic along the reinforcing glass
fibres, if the surface is eroded or scratched and then immersed in
water. In this case, allow adequate time for the coating to dry
prior to testing.
Rubber linings: These may be slightly conductive due to their 
carbon content. As with other conductive coatings, reduce the
sensitivity so that the detector indicates a known flaw but does
not sound when the probe is placed on sound coating. It may
also be necessary to increase the test voltage to compensate for
the current flow through the coating.
Coating may not be fully cured: In this case the coating still

contains solvents which allow the path to the high voltage to be
formed even if a flaw is not present. To overcome this problem,
allow the coating to cure before undertaking the test.
14.2 CONCRETE SUBSTRATES
If a concrete or cement substrate contains enough moisture, then it will
conduct electricity and the holiday detector can be used to detect flaws
in its coating.
The procedure is generally the same as that described in 'Preparing
For Test' on page en-14 and 'Test Procedure' on page en-16, but the
following points should be noted. Hammering a masonry nail, or
similar conducting spike, into the concrete or cement makes the earth
signal return contact.
www.elcometer.com
R
en-24