According to a 2026 technical paper by NACE International, corrosion under insulation (CUI) remains a leading cause of piping failures in the process industry. CUI occurs when moisture trapped beneath insulation attacks the pipe wall, often at temperatures between -4°C and 175°C.
Carbon steel piping is most susceptible, especially at supports, flanges, and valves where insulation details are difficult to seal. The mechanism is accelerated by chlorides in insulation materials or external contaminants, leading to pitting and stress corrosion cracking.
Key prevention measures include:
• Using closed-cell insulation or hydrophobic coatings.
• Applying aluminium foil or stainless steel jacketing with proper sealants.
• Designing insulation supports to allow drainage and airflow.
• Implementing regular inspection intervals with guided wave ultrasonic testing.
Per the paper, proactive coating selection and design for drainage can reduce CUI risk by over 80%. Auditors now check compliance with NACE SP0198 and ISO 12944 during plant inspections.
How does your team address CUI in older piping systems?
Source: NACE International, 2026