Procedure for Conducting Contactless Measurement of Coating Thickness Using Terahertz Technology

This test method describes a process for determining the uniformity and conformance to minimum/maximum specified thickness of coatings applied to newly manufactured steel pipe in a shop using noncontact electromagnetic gauges (NEMG) equipped with terahertz technology.

The procedures for in-line accuracy verification and adjustment of the NEMG are described herein.

This document contains the following appendices:

• Appendix A (nonmandatory) – Theory of Coating Thickness Measurement Using NEMG Equipped with Terahertz Technology

• Appendix B (nonmandatory) - Accuracy Verification using an In-line Internal Standard Sample

NEMGs that use terahertz technology are not currently reflected in SSPC-PA 2 and ASTM D7091 and are not currently recognized by steel water pipe coating industry standards including AWWA C222 and AWWA C210. Given the unique processes involved (including non-contact) and the volume of coating thickness data acquired in-line, it is not prudent to revise existing coating thickness measurement standards to include this method of measurement and data acquisition.