【国外标准】 Standard Test Method for Concentration of Pinhole Detections in Moisture Barriers on Metal Jacketing

5.1 Corrosion on the interior surface of metal jacketing can be caused by the formation of a galvanic cell between the dissimilar metals of the pipe and jacket or by crevice or pitting corrosion.5.2 The application of a moisture barrier to the interior surface of the metal jacketing inhibits this corrosion by interfering with the galvanic cell formation or by preventing water from contacting the interior metal surface.5.3 Holes in the moisture barrier decrease its effectiveness in preventing corrosion. Large holes, scratches, or tears in the moisture barrier visible to the naked eye are easily discerned and are cause for rejection of the metal jacketing.5.4 Small holes called pinholes or holidays that are not visible to the naked eye but are large enough to allow corrosion are a significant concern and should be avoided to the extent possible.5.5 This test method is used to quantify the concentration of pinhole detections present in a moisture barrier for the purpose of quality control on metal jacketing with an applied moisture barrier.5.6 Examples of standards which have specific requirements for the maximum allowable concentration of pinhole detections in the moisture barrier are Specifications C1729 and C1767.1.1 This test method covers the determination of the concentration of pinhole detections in a moisture barrier film or coating that is applied to the interior surface of metal jacketing.1.2 Since this method relies on the completion through the metal jacketing of an electrical circuit, this method is only applicable to jacketing that is electrically conductive and has a moisture barrier applied which is not electrically conductive.1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.