4.1 Insulations that are used as a part of the thermal insulation system in contact with austenitic stainless steels have the potential to become contaminated with water soluble corrosive ions which, in turn, if permitted to reach the stainless steel surface, are possible to contribute to external stress corrosion cracking (ESCC). Therefore, it is important to reduce the exposure of such insulating materials to water-soluble corrosive ion compounds at all stages of manufacture, handling, shipping, storage, and application. During manufacture, precautions shall be taken to minimize water soluble corrosive ion content, both in the material and as surface contamination. Once the manufacture is complete, care must be exercised during handling, transporting, shipping, storage, receiving, and application to avoid contamination with corrosive ions that can be transported by water through the insulation materials onto the stainless steel surface. This practice presents criteria which, if followed, will minimize the risks of ESCC associated with the application of insulation materials. It must be emphasized, however, that because of the many variable factors present, complete freedom from ESCC can not be assured under all circumstances, even when following the guidance of this practice.

4.2 Continued protection of the insulation and the stainless steel surface from moisture and contamination after the insulation system is installed and over its entire service life is of significant importance. In-service contamination has the potential to occur from many sources; for example, from airborne contaminates, rain or salt spray, periodic fire sprinkler system tests, wash-downs, or process leakage. Weather barrier jacketing systems and proper application shall be chosen to provide long-term protection in the intended use environment.

4.3 The entire insulation system shall be periodically inspected and maintained. Insulation that is suspected of contamination shall be retested or immediately replaced. Wash down of insulated pipe and equipment shall be avoided. Whenever possible, protective coatings or finishes shall be applied directly to the stainless steel surface as the primary source of corrosion protection.