Corrosion Under Insulation Repair and Protection

Identify, Repair, and Prevent Corrosion Under Insulation.

Corrosion under insulation, or CUI, is one of the most persistent threats to insulated industrial assets. It occurs when moisture penetrates insulation systems and becomes trapped against piping or vessels, leading to corrosion beneath the surface. Water can enter through rain, leaks, washdowns, deluge systems, or condensation caused by temperature cycling and low-temperature operations such as refrigeration units.


Because CUI develops out of sight, it often remains undetected until insulation is removed or leaks and failures occur, by which point significant wall loss or pitting may already be present. This hidden nature makes CUI a widespread challenge across industries including refining, petrochemical, power generation, and both onshore and offshore operations.


Our CUI services are designed to identify damage early, restore compromised areas, and apply durable protective systems that extend asset life. We use a range of Belzona polymeric composites, carefully matched to your specific operating conditions and asset requirements. These systems can be safely applied in-situ—even on hot surfaces.


By combining targeted repair methods with high-performance protective solutions, we help facilities take a proactive approach to managing CUI.

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FAQs

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  • What Causes CUI?

    CUI is caused by a combination of moisture, temperature, and time. When water enters an insulation system and remains in contact with metal surfaces, especially at certain temperature ranges, it creates the conditions for corrosion. Oxygen enables corrosion in carbon steel, while chlorides can contribute to cracking in stainless steel. Contaminants like salts, acids, and other chemicals can further accelerate the damage.

  • Where does corrosion under insulation (CUI) commonly occur?

    CUI can develop on any insulated equipment exposed to moisture, but it is most commonly found on piping, tanks, pressure vessels, and high-temperature steel systems. It is especially prevalent in industries such as refining, petrochemical, power generation, and other industrial environments, including both onshore and offshore facilities.

  • What is your approach to CUI repair and protection?

    Our approach follows four key steps: assess, repair, protect, and plan. We start by evaluating assets for hidden corrosion and damage, then restore affected areas using engineered repair materials. Next, we apply high-performance protective coatings suited to the operating conditions. Finally, we help implement an inspection and maintenance plan to monitor assets and prevent future problems.

  • Can CUI be repaired without removing the equipment from service?

    In many cases, yes. Certain repair system, such as polymeric composite materials, can be applied in-situ, even on hot surfaces, allowing repairs to be completed without shutting down operations. This helps minimize downtime.

  • How can corrosion under insulation (CUI) be detected?

    CUI is typically detected through a combination of visual inspection, insulation removal in high-risk areas, and non-destructive testing methods such as ultrasonic thickness testing or radiography. Because corrosion is hidden beneath insulation, a targeted inspection strategy is incredibly important. 

Addressing CUI from Start to Finish

Corrosion under insulation isn’t usually a one-time issue. It tends to develop slowly over time, often going unnoticed until insulation is removed and the damage is already more advanced than expected. This is something we regularly see across industrial facilities in Houston and the surrounding Gulf Coast.


Because of this, early identification is very important. Focusing on high-risk areas, such as equipment exposed to moisture or operating within certain temperature ranges, can help stay ahead of potential issues. For many Houston-area plants, refineries, and commercial facilities, this kind of proactive approach is instrumental to maintaining asset reliability.


Once corrosion is found, the goal is to address it quickly and correctly the first time. Repair systems need to match the service conditions, especially when dealing with high heat, limited access, or the need to keep equipment in service. In many cases, engineered solutions like polymeric composites can restore damaged areas without requiring full replacement, making them a practical option for industrial painting and maintenance projects in Houston and surrouding areas.