Corrosion Under Insulation (CUI) is a type of corrosion that occurs in piping and equipment protected by thermal insulation. This phenomenon is especially problematic in the petrochemical, refinery, and chemical processing industries, where pipes are frequently exposed to harsh environmental conditions. Below, we highlight the key aspects of CUI:

🔸 Causes of Corrosion Under Insulation

💧 Moisture: The primary cause of CUI is water penetration. Insulation can trap water from sources such as rain, condensation, or washdowns. Once water enters the insulation, it can remain trapped against the pipe’s surface, promoting corrosion.

🌡 Temperature: CUI is most likely to occur at temperatures between -4°C and 175°C, as this range allows water condensation to form.

⚙️ Type of Insulation: Certain types of insulation, especially those containing chlorides or hygroscopic materials (which absorb moisture), can accelerate corrosion.

💨 Process Leaks: Fluids containing corrosive agents can leak from within pipes and accumulate under the insulation, further increasing the risk of CUI.

🔸 Effects of CUI

CUI can lead to:
⚠️ Significant reduction in pipe wall thickness
⚠️ Loss of mechanical strength due to material degradation
⚠️ Unexpected plant shutdowns to identify and replace damaged sections

🔸 Prevention & Mitigation Strategies

🔎 Selecting Proper Insulation Materials: Using non-hygroscopic, chloride-free insulation minimizes the risk of CUI.

🚰 Drainage System Design: Ensuring effective drainage in the insulation system helps prevent water accumulation.

🛡 Protective Coatings: Applying corrosion-resistant coatings to the pipe surface before insulation installation provides an extra layer of defense.

🔧 Regular Maintenance & Inspection: Periodic monitoring and maintenance can detect and address CUI issues before they lead to major failures.

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