-M/1 Holiday Detector- INFORMATION BULLETIN |
|
The
electrical holiday detector commonly used for inspection for brushed, sprayed or
dip-applied protective coatings is considered a non-destructive device with a
source of less than 75 volts applied to the coatings using an electrode
consisting of a cellulose sponge dampened with an electrically conductive liquid
such as tap water. The electrode
pushes a film of liquid over the surface and when a holiday is encountered,
current will flow through the liquid to the metal. An audible indicator is used to signal coating defects. Recommended
points to be included in a specification for the electrical inspection of thin
film coating with the so-called “non-destructive” type holiday detector,
Tinker & Rasor Model M/1 are: 1.
The voltage between the electrode (sponge) and the metal surface upon
which the coatings lies should not exceed 75 volts measured between the
electrode sponge and the coated metal when the detector is in it’s normal
operating position. 2.
An electrical connection must be made from the detector to some bare spot
on the metal structure to be coated. 3.
The holiday detector should be equipped with an audible signal which is
responsive to high current flows between electrode and the metal surface. 4.
The coated surface should be dry prior to making the inspection and if
the surface is in an environment where electrolytes might form on the surface
such as salt spray, the coated surface should be washed with fresh water and
allowed to dry. The
consensus of the industry is that ordinary tap water will suffice to wet the
sponge electrode when this type of electrical holiday inspection is conducted on
protective coatings up to 10 mils in thickness.
On film thickness between 10 and 20 mils a non-sudsing type wetting agent
added to the water is recommended. This
allows for faster penetration of the liquid into pinhole defects.
A wetting agent such as TINKER & RASOR’S “WATER-WETTER”
is an excellent product for this purpose. Available
in 8 ounce size bottle. It is
further agreed that this type holiday detector is not satisfactory for
inspection of protective coatings over 20 mils in thickness and completely
ineffective on prefabricated coatings such as PVC, etc. An
electrical holiday detector should be used at the time the coating is applied.
The holiday detector should never be used to evaluate the quality or
usefulness of a coating and should be used only as an aid in the application of
the coating. When the detector is
used at the time of application, holidays can be readily located and repaired.
The detector not only locates holidays, but it enables the applicator to
develop techniques of better application. All instruments being returned for repair should be sent PREPAID to either address below:
Include with shipment information the nature
of the problem, purchase order, serial number |
|
T&R
Product Instructions M/1
Pinhole Detector
|