Insulations that are used as a part of the thermal insulation system in contact with austenitic stainless steels may become contaminated with water soluble chloride ions which, in turn, if permitted to reach the stainless steel surface, could contribute to external stress corrosion cracking (ESCC). Therefore, it is important to reduce the exposure of such insulating materials to water-soluble chloride ion compounds at all stages of manufacture, handling, shipping, storage, and application. During manufacture, precautions shall be taken to minimize water soluble-chloride 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 chloride 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 should 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.

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 can 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 should be chosen to provide long-term protection in the intended use environment.

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