scope:

General

This NACE standard provides a nondestructive method for the detection of holidays in a nonconductive coating film that has been applied to the inner wall of oilfield tubular goods. The apparatus and the recommended procedure for conducting the test are described, as are methods of reporting the test data.

The test method applies to coatings that have a specified maximum dry-film thickness of 250 μm (10 mils). It is valid for coatings that have not been in service or previously tested with a salt solution. When holiday testing is performed on coatings that have been in service or that have been previously tested for holidays with a salt solution, there is a possibility of misleading results arising from surface contamination or salt bridging. The coating surface shall be free of materials that give added electrical insulation or that can mechanically damage the coating during the test.

A "holiday" is defined as a discontinuity in a protective coating that exposes unprotected surface to the environment. For this test method, it means an area of applied coating that exhibits electrical resistance of less than some specified value when that area is contacted with a wet sponge and detected with an appropriate instrument.

The specified resistance for holiday detection is 80,000 ohms ±10% when measured between the wet probe sponge and the pipe substrate.

Several internal tubular coatings have a manufacturers' specified thickness range of 200 to 330 μm (8 to 13 mils). These coatings shall be tested with a wet sponge at 67.5 V (DC) and 80,000 ohms (±10%) resistance.