Corrosion Under Insulation (CUI): Causes, Risks & Prevention

Corrosion under insulation, or CUI, is one of the most expensive and hardest-to-detect failure modes in industrial piping. It happens when moisture becomes trapped between the pipe wall and its insulation jacket, then sits against bare or coated steel for months or years, quietly thinning the pipe wall until it fails — often without any visible external sign until a leak or rupture occurs.

Why Qatar and the UAE Are Especially Exposed

Coastal humidity, seasonal condensation, and the extreme day-to-night temperature swings across Qatar and the UAE all increase the rate at which moisture can migrate into an insulation system. Combined with high ambient salinity near the coast, any breach in the cladding envelope becomes an accelerated corrosion site rather than a slow one.

Where CUI Typically Starts

• Poorly sealed jacket overlaps and longitudinal seams
• Termination points at flanges, valves, and pipe supports
• Damaged or punctured cladding from foot traffic or maintenance work
• Caulking and sealant that has degraded under UV exposure

How Properly Engineered Cladding Prevents It

The single most effective CUI defense is a hermetically sealed metal cladding system: lock-seam joints, silicone-sealed overlaps, and vapor-retarder jacketing selected to ASTM C1136 that leaves no path for moisture ingress. Removable, quick-release insulation boxes at valves and flanges are equally important, since these access points are where most standard installations fail first — forcing maintenance crews to cut into fixed cladding and never properly reseal it.

On our own projects across Qatar and the UAE, this combination of design discipline and CNC-precision fabrication has delivered a 0% recorded CUI rate to date. See our pipe and tank cladding services for the materials and standards we specify on each project type.