Conventional NDT
Coating holiday testing
A coating protects steel only where it is continuous. A pinhole, or holiday, lets the electrolyte reach the steel and concentrates corrosion at that point. Holiday testing finds those discontinuities in tank linings, vessel linings and pipeline coatings before the asset goes into service, while repair is still easy.
Low-voltage and high-voltage methods
- Low-voltage wet sponge: for thin-film coatings, typically up to the thickness limit in the standard; a damp sponge completes a circuit through any holiday.
- High-voltage spark (DC or pulse): for thicker coatings; the test voltage is set from the coating thickness so that it jumps holidays without damaging sound coating.
Setting up the test correctly
The test voltage and method depend on the dry film thickness and the coating manufacturer’s guidance, so thickness is measured first. The coating must be fully cured, and the steel grounded. Each holiday found is marked, repaired and re-tested.
Typical applications
- Internal linings of storage tanks and process vessels.
- Pipeline coatings at the yard and before lowering-in.
- Field joint coatings and repairs.
How we deliver it
Coating holiday testing is carried out to a written procedure approved for the scope, naming the code and edition, the equipment and calibration, the coverage and the acceptance criteria. The procedure and each technician’s certification are submitted for the client’s review before mobilisation.
Work is planned and supervised by ASNT Level III personnel; our founder holds ASNT NDT Level III in UT, RT, MT, PT and VT. Reports state the coverage achieved and any limitations, so the engineer reading them knows what was examined and what was not, and any reportable finding is raised the same day.
Governing codes and standards
- NACE (AMPP) SP0188 (holiday testing of new protective coatings on conductive substrates)
- NACE (AMPP) SP0274 (high-voltage inspection of pipeline coatings)
- ASTM D5162 (holiday testing of non-conductive coatings on metallic substrates)
- ISO 29601 (assessment of porosity in protective coatings)
What you receive
- Test record with method, voltage, coating thickness and instrument calibration
- Holiday locations and repair verification
Industries served
- Storage tanks and terminals
- Pipelines
- Water and wastewater
- Chemical and petrochemical
Frequently asked questions
How is the holiday test voltage chosen?
From the measured dry film thickness and the standard being applied (for example NACE SP0188), together with the coating manufacturer’s guidance, so the spark jumps holidays without damaging sound coating.
Talk to an inspection engineer
Send the equipment list or drawings, the inspection you need and your timing. Quotes are prepared for each scope and region.
Request a QuoteRequest an inspection quote (RFQ)
Tell us the asset, the method, where it is, the governing code, your dates, the size of the job and the report you need. We reply with questions or a quote. Affordable, accessible, fully customizable — no published pricing.
Or email the same details to info@atlantisndt.com. Mobilisation: North America; confirm your location in your RFQ.
Speak to an ASNT NDT Level III
Atlantis NDT provides ASNT Level III consulting, NDT training to ASNT SNT-TC-1A, inspection management software and independent report validation. Request a free consultation and we will return a tailored quote — affordable, accessible and fully customizable to your programme.