# ASTM D4787

Source: https://coatmentor.com/standards/astm-d4787/ · Updated 2026-10-14

Continuity (holiday) testing of linings on concrete.

**Publisher**: ASTM International

**Area**: Concrete

ASTM D4787 covers spark testing of new non-conductive linings on concrete, to find pinholes, voids, holidays and cracks. The current edition is D4787-24.

## Why concrete is different

Steel conducts; concrete conducts only through its moisture, rebar and make-up. The inspector therefore first checks that the concrete, or a conductive primer laid under the lining, can carry the test current. The ground lead goes to rebar or another permanent metal ground, or to a wet sandbag on the concrete.

## In practice

- Use a pulsed or continuous DC high-voltage tester at the voltage the standard's method gives for the thickness.
- Move the electrode at about 0.3 m/s (1 ft/s) and mark each indication for repair.
- Test only new linings: a lining that has been in immersion can be damaged by the spark or give false readings.
- Solvent left in a fresh lining can ignite. Test only when it has cured enough.

**3** practice items in the members area mention ASTM D4787 (CIP 2: 3).

## Related

- **Concepts:** [Holiday (discontinuity) testing](https://coatmentor.com/learn/holiday-testing/)
- **Standards:** [NACE SP0188](https://coatmentor.com/standards/nace-sp0188/) · [ASTM D5162](https://coatmentor.com/standards/astm-d5162/) · [ISO 29601](https://coatmentor.com/standards/iso-29601/) · [NACE SP0892](https://coatmentor.com/standards/nace-sp0892/)
- **Defects:** [Outgassing](https://coatmentor.com/defects/outgassing/)

## About this page

This page describes the subject of ASTM D4787 in our own words; it does not reproduce the standard. For the full text, buy the current edition from ASTM International. Checked on 2026-10-14; errors go in the [corrections log](https://coatmentor.com/method/). CoatMentor is an independent study aid. It is not affiliated with ISO, AMPP, SSPC, NACE International, ASTM or FROSIO.