Stainless Steel Pipe Insulation Barrier Corrosion Resistant Applications

Insulation materials used for stainless steel pipes and vessels contain chlorides. If this insulation is exposed to moisture, chlorides may be released into the moisture layer on the surface of the pipe or container, potentially causing pitting or stress corrosion cracking.
While pitting and stress corrosion due to heat and moisture insulation is an important factor, the choice of pipe or vessel material will depend on the nature of the fluid carried within the pipe or the processes occurring within the vessel.
Although insulation materials contain chloride, leachable levels of chloride may be as low as 10 ppm. Despite low levels of leachable chloride and the inclusion of corrosion inhibitors (e.g. sodium silicate) in some formulations, pitting and stress corrosion can be observed in insulated stainless steel pipes and vessels.
Regardless of the initial chloride content in the insulation, the presence of moisture can concentrate chloride in localized areas and cause corrosion of stainless steel surfaces. The chloride content in the insulation can also be enhanced from external sources (such as rainwater, detergents or process water) or through evaporation. In fact, rainwater, washing or processing water can contain up to 10 to 100 times the amount of chloride that can leach from insulation materials. This increase in chloride levels may occur when insulation is applied and during storage prior to use.
The combination of moisture, low oxygen levels, chloride concentrations and insulation temperatures can cause pitting corrosion. Stress corrosion cracking is unlikely to be a factor at temperatures below 50°C, but can be an important feature in the temperature range of 50°C to 150°C.
For stainless steel pipes and vessels that are not exposed to moisture (such as under warm, dry conditions inside), no corrosion barrier is required. However, if the insulation is likely to become damp, it is recommended that a corrosion barrier be applied to the pipe or vessel before the insulation is applied.
Two types of anti-corrosion partitions with insulation made of waterproof paint can be used: suitable paint (e.g. high-temperature silicone type) or 0.06mm thick aluminum foil. Aluminum foil is actually better to use because of its ease of use. This corrosion barrier should be applied in accordance with BS 5970 - Code of Practice for Thermal Insulation of Pipes and Equipment.