NACE TM0186

Abstract

Scope: This NACE standard provides a nondestructive test method for the detection of holidays in a nonconductive coating film that has been applied to the inner wall (bore) of oilfield metallic tubular goods. The apparatus and the procedure for performing the test are described, as are methods of reporting the test data.  The test method applies to coatings that have a specified dry-film thickness of 355 to 760 μm (14 to 30 mils). It is valid only 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 may mechanically damage the coating during the test. This test method is not intended as a means of predicting the service life or service performance of these coatings. A “holiday” is defined as a discontinuity in a protective coating that exposes unprotected surface to the environment. For the purposes of this test method, it means an area in an applied nonconductive coating that exhibits electrical conductivity when exposed to a known impressed voltage.  The voltage range for holiday detection shall be 4 to 12 V direct current (DC) per μm (100 to 300 V [DC] per mil) of dry-film thickness. The test voltage is determined by the type of probe, the maximum specified dry-film thickness, the type of coating application, and the customer. The voltage shall be measured between the probe and the metallic tubular good.