Sponge holiday detector – SAHD-WS03

The sponge holiday detector is used to check the continuity of thin insulating coatings applied to conductive substrates. By means of a low-voltage inspection, it can detect pinholes, porosity and discontinuities extending through the coating that may compromise the protection provided by paint or a protective coating.

During inspection, the wet sponge probe is moved across the coated surface while the earth lead is connected to the conductive substrate. When the coating is continuous, the insulating layer prevents the electrical circuit from closing. If the sponge encounters porosity, a pinhole or another through-coating discontinuity, the liquid reaches the underlying substrate and allows current to pass: the instrument then signals the affected area through visual and audible alarms.

The holiday detector for thin coatings is intended for insulating coatings up to 500 µm thick. It is therefore suitable for inspecting protective films, thin paint systems and coatings applied to metal surfaces or other conductive substrates compatible with the method. The inspection does not measure coating thickness or assess general coating wear; it checks for discontinuities that interrupt the electrical insulation of the coating.

Compared with holiday detectors using a metal probe and intended for thicker coatings, the wet sponge model operates at low voltage and is specifically designed for thin layers. The choice between a wet sponge holiday detector and a higher-voltage holiday detector must be based on coating thickness, surface characteristics and the applicable inspection procedure.

Wet sponge testing is used to check protective coatings applied to metal components, sheet metal, structures, tanks and pipelines. On coated pipelines, it makes it possible to locate pinholes or discontinuities in thin coatings before commissioning or during inspection and maintenance activities.

The use of a sponge holiday detector is particularly useful where coated surfaces must be checked without using a high-voltage method. The wet sponge probe allows the inspection to be carried out across the surface, quickly identifying areas where the coating does not maintain the required insulating continuity.

For discontinuity testing of non-conductive protective coatings applied to metallic substrates, the wet sponge method refers to ASTM D5162, Method A. For inspection of thin coatings used to protect pipelines, the applicable reference is ASTM G62, Method A.

For specific applications involving vitreous and porcelain enamel coatings applied to metallic substrates with non-profiled surfaces, low-voltage testing refers to ISO 8289-1. The instrument can also be used for checks on epoxy-coated steel bars, wires and welded fabric intended for concrete reinforcement, an application associated with ISO 14654.

The sponge holiday detector is therefore a dedicated solution for detecting porosity and pinholes in thin insulating coatings on conductive substrates, providing a practical and immediately readable inspection through visual and audible indication. A calibration report is available on request.

Applications

• Verification of thin insulating-coating continuity on conductive substrates
• Detection of porosity, pinholes and through-coating discontinuities in protective coatings
• Low-voltage holiday testing on paint systems and insulating films up to 500 µm
• Inspection of metallic components, sheet metal, structures and coated surfaces
• Verification of thin coatings applied to pipelines
• Production, maintenance and component-acceptance checks
• Inspections in accordance with ASTM D5162, Method A, on protective coatings applied to metallic substrates
• Inspection in accordance with ASTM G62, Method A, on thin pipeline coatings
• Specific applications on vitreous and porcelain enamel coatings in accordance with ISO 8289-1
• Checks on epoxy-coated steel reinforcement for concrete applications within the scope of ISO 14654

FAQ – Sponge holiday detector

What is a sponge holiday detector used for?
It is used to verify the continuity of thin insulating coatings applied to conductive substrates, identifying porosity, pinholes and through-coating discontinuities that may compromise surface protection.

How does inspection with a sponge holiday detector work?
The wet sponge probe is moved across the coated surface while the earth lead is connected to the conductive substrate to allow the electrical circuit to close. When the sponge encounters porosity, a pinhole or another discontinuity that interrupts the coating insulation, the liquid reaches the underlying substrate and the instrument generates a visual and audible alarm.

What does wet sponge holiday detector mean?
It is the English term for a sponge holiday detector: an instrument that uses a wet probe and low voltage to identify discontinuities in thin insulating coatings applied to conductive surfaces.

Which coatings can it be used on?
It is suitable for thin insulating coatings up to 500 µm, including protective films and paint systems applied to metallic substrates or other conductive surfaces compatible with the method.

Does a sponge holiday detector measure coating thickness?
No. The instrument identifies discontinuities that interrupt the insulating continuity of the coating. A dedicated coating thickness gauge is required to measure coating thickness.

What is the difference between a sponge holiday detector and a high-voltage holiday detector?
A sponge holiday detector uses low voltage and is intended for thin coatings up to 500 µm. Holiday detectors with a metal probe and higher operating ranges are more suitable for thicker insulating coatings or applications requiring a different inspection configuration.

Can it be used to inspect coated pipelines?
Yes. It is suitable for checking thin coatings applied to pipelines, identifying porosity or pinholes that may interrupt the continuity of the protective coating.

Why is the low-voltage method used?
The low-voltage wet sponge method is suitable for thin coatings because it identifies through-coating discontinuities by closing the electrical circuit at the defect location.

Which standards apply to the sponge holiday detector?
For non-conductive protective coatings applied to metallic substrates, the wet sponge method refers to ASTM D5162, Method A. For thin coatings applied to pipelines, the reference is ASTM G62, Method A.

Can a calibration report be requested for the sponge holiday detector?
Yes. A calibration report is available on request and helps document instrument management within company quality-control procedures.