With stainless steels, problems have resulted because of leachable chlorides contained in some insulation. For the 300 series stainless, use insulation that meets MIL-I-24244 or ASTM C-795 specifications. This provides sufficient control, unless there is an external invasion of chlorides.

A further way to reduce the chance of chloride attack is to use an inhibited insulation. Other points should also be considered:

1. With some insulation, such as polyurethane, it is not possible to add inhibitors. Thus, fire-retarded polyurethanes are not recommended for use over austenitic stainless steels.
2. For specifications that require less than 10 ppm of chloride in the insulation, attention must be paid to the mortars and cements used, since these may contain chlorides.
3. To prevent water and chlorides from reaching the stainless steel, the external barrier must be designed properly and maintained periodically.

When steam tracing is used within insulation, extra precautions are needed to resist stress-cracking corrosion.

Be sure that stainless steel is not coated. In case of a fire, catastrophic embrittlement could result if zinc, titanium or other metallics were used in previously applied paints.

The metal jacketing should be securely fastened and banded to prevent water entry at joints, or where the insulation is supported with attachment angles. Cement-coated insulation can be finished with a suitable waterproof mastic to prevent water ingress. The type of insulation and method of application chosen should assure the absence of shrinkage cracks.

Wrapping equipment with aluminum foil before applying insulation will reduce the risk of corrosion, since the foil provides a physical barrier that prevents the saturated chloride solution from reaching the metal surface. Due to its high thermal conductivity, the aluminum will be at substantially the same temperature as the equipment, and the chloride solution will shift to the foil, rather than the stainless.

When steam tracing is used within insulation, extra precautions are needed to resist stress-cracking corrosion. Extra protection via insulation selection or use of foil wrap is necessary to protect the costly stainless steel surface.