Corrosion under insulation is the most expensive insulation problem in industry, and it is almost entirely a consequence of how insulation behaves when it gets wet rather than of how well it insulates when dry.
The mechanism is simple. Water enters through a cladding defect, a damaged sealant joint or a penetration. Conventional fibrous insulation absorbs and holds it against the pipe. The annular space is now hot, wet and oxygenated, which is close to the ideal condition for accelerated corrosion of carbon steel. The insulation also hides the damage, so the first evidence is often a leak or a thickness survey that comes back far worse than expected.
The temperature range that does the damage
CUI risk is highest where the metal temperature keeps the water liquid rather than boiling it off. Lines that run continuously hot and dry are relatively safe. The dangerous cases are lines that cycle, lines that sit in the intermediate range, and lines that are intermittently in service. Cold service has its own version of the same problem driven by condensation rather than ingress.
What actually reduces the risk
- Use insulation that is hydrophobic through its full thickness, not just at a facing, so a cut edge or puncture does not create a wet path
- Reduce the number of layers and joints, because every joint is a potential ingress point
- Keep the outer diameter small so cladding spans are shorter and less prone to distortion
- Detail penetrations, supports and terminations properly, since these are where most ingress starts
- Choose a system that can be opened for inspection and refitted, so surveys actually get done
Why aerogel helps
Aerogel blankets are hydrophobic throughout, so liquid water is repelled while water vapour can still escape. A damaged section does not wick water along the run, which keeps damage local and inspectable. Because the same thermal performance is achieved in far less thickness, there are fewer layers, fewer joints and less cladding to fail. None of that makes CUI impossible, but it removes the mechanism that turns a small cladding defect into metres of ruined pipe.
Related products
- Nar-650High‑Temperature Aerogel Blanket
- Pipe Section PS-Hot
- Aerogel Blanket AB-FR
Talk to us about your project
Send us your line list, drawings or target U-values and we will come back with a thickness recommendation, a bill of material and a quotation. Contact our technical team.
