Detection and correction of defects in protective coatings are important factors in an effective corrosion control program. High voltage electrical inspection of pipeline coatings prior to installation is one method in general use. Prior to issuance of this NACE standard, there has been no U.S. standard for electrical inspection of fusion-bonded epoxy pipeline coatings. Although several specifications have been written by operating companies for high voltage electrical inspection of protective coatings, they apply only to specific coatings.

This standard recommended practice was prepared by NACE Work Group T-10D-9c on Electrical Inspection and its parent, Task Group T-10D-9 on Coating Inspection, a component of Unit Committee T-10O on Protective Coating Systems. This standard, issued by NACE under the auspices of Group Committee T-10 on Underground Corrosion Control, was developed through the joint efforts of representatives of coating manufacturers and applicators, holiday detector equipment manufacturers, corrosion specialists, and others concerned with the construction of underground pipeline facilities, as represented in NACE Unit Committee T-1 OD. The recommendations contained herein apply only to fusion-bonded epoxy pipeline coatings, which generally are applied to a dry film thickness of 10 to 30 mils (0.25 to 0.76 mm). For other types of patching materials and joint wrap, please consult the appropriate manufacturer of the material for holiday detection voltages. Adherence to the principles of this standard will improve methods of holiday detection and, therefore, the effectiveness of the coating.

1.1 This recommended practice presents accepted techniques in the use of holiday detector equipment currently used on fusion-bonded epoxy pipeline coatings prior to on-site installation of the pipeline. It also presents recommended voltages for various coating thicknesses (see Table 1).

1.2 Electrical inspection (holiday detection) is a test of the continuity of a protective coating. This type of inspection is not intended to provide information on coating resistivity, bond, physical characteristics, or the overall quality of the coating. It will detect voids, cracks, foreign inclusions, or contaminants in the coating that are of such a size, number, or conductivity as to significantly lower the electrical resistance or dielectric strength of the coating.

1.3 Use of a holiday detector shall be under the direction of a qualified coating inspector, such as an NACE Certified Coating Inspector. An initial holiday detector inspection, performed as soon as practical after the application of the coating, will assist in verifying adherence to specifications for the materials and the application procedures. A final electrical coating inspection, before the coated pipe is placed in the ground, will disclose coating discontinuities or damage that may have occurred during the shipping, storage, or construction period.

Historical Document 1990