Corrosion under insulation (CUI) is a hidden problem in many industrial facilities. It weakens pipes, tanks, and other insulated systems, often without being noticed until the damage becomes severe. This issue becomes even more troublesome during cold months when condensation and temperature swings speed up corrosion.

At Axtell Services, we’ve seen firsthand how CUI can shut down systems, cause expensive repairs, and threaten safety. This article explains what causes corrosion under insulation, how cold weather affects it, and what facility managers need to know to reduce the risk.

What Is Corrosion Under Insulation?

CUI is a type of external corrosion that occurs on metal surfaces beneath insulation materials. It usually affects carbon steel or low-alloy steel used in industrial plants, refineries, and power facilities.

The process begins when water gets into the insulation. This often happens through damaged jacketing, failed sealants, or poor design. Once inside, moisture stays trapped against the metal surface, creating a corrosive environment.

Unlike visible rust, this form of corrosion hides under layers of insulation and jacketing. By the time leaks or failures appear, the structure may already be compromised.

Why Cold Weather Makes CUI Worse

Many assume corrosion is mostly a warm-weather issue. In reality, freezing temperatures introduce new problems that speed up CUI.

More Condensation

When warm equipment runs in a cold environment, the difference in temperature causes condensation. This is common on outdoor piping and tanks, especially during freeze-thaw cycles. Moisture forms and becomes trapped under insulation, where it lingers.

Ice Damage

If water freezes within the insulation, it expands. This expansion pushes apart seams, adhesives, and jacketing. As the ice melts, water seeps in deeper and restarts the cycle.

Fewer Maintenance Checks

Snow, ice, and cold temperatures slow down inspection routines. Crews may not remove insulation during winter, which delays discovery of hidden damage. This gives corrosion more time to develop.

High-Risk Areas for CUI in Winter

Some areas are more vulnerable to corrosion under insulation during cold months.

  • Outdoor piping exposed to rain, snow, or meltwater
  • Storage tanks with fluctuating temperatures
  • Piping elbows, joints, and valves where insulation fits poorly
  • Supports and welded areas where seams often fail
  • Aging equipment with old insulation or broken jacketing

Facilities that rely on steam systems, heated liquids, or outdoor process lines face the highest risk.

Why It Often Goes Unnoticed

Corrosion under insulation is called the “silent killer” for a reason. Since it’s hidden beneath multiple layers, it often progresses unnoticed. Even trained personnel can miss it without proper tools or access.

Routine walk-throughs and visual checks don’t always catch early signs. During winter, insulation is rarely removed unless failure is suspected. That delay gives moisture more time to break down metal surfaces.

Warning Signs to Watch For

Although the corrosion itself is hidden, some surface clues suggest possible CUI.

  • Wet or sagging insulation
  • Warped or dented jacketing
  • Signs of mold, mildew, or staining
  • Sudden pressure loss or system leaks
  • Drops in performance of heating or steam systems

These symptoms call for professional inspection before further damage occurs.

How Axtell Services Identifies and Manages CUI

Axtell Services works with commercial and industrial facilities to locate and manage corrosion under insulation. Our approach is built on experience, proper equipment, and safe application of industrial coatings.

Inspection and Testing

We conduct thorough assessments during scheduled shutdowns or when systems are safe to access. This may include thermal imaging, moisture detection, or targeted insulation removal in high-risk areas.

Insulation Removal

Our crews remove insulation and jacketing where needed to expose the surface underneath. We take precautions to limit mess and contain debris, even in active facilities.

Cleaning and Surface Prep

Once exposed, metal surfaces are cleaned using methods like abrasive blasting or power tool prep. We remove scale, rust, and residue to prepare the surface for coating.

Protective Coating Application

We use high-performance industrial coatings designed to resist water and chemicals in insulated environments. This may include zinc primers, epoxy barrier coatings, or urethane topcoats, depending on the conditions.

Reinsulating and Jacketing

After recoating, we reinstall insulation using moisture-resistant materials and proper sealing. This prevents future water intrusion and protects the system for years to come.

The Cost of Waiting Too Long

Ignoring corrosion under insulation can lead to serious outcomes.

  • Unplanned shutdowns and system failure
  • Dangerous leaks or safety risks
  • Repair costs that exceed planned maintenance budgets
  • Regulatory citations for failing inspections
  • Lost production and operational downtime

Catching corrosion early protects equipment and keeps facilities running on schedule.

Steps to Prevent CUI in Cold Weather

During winter, extra steps are needed to stop corrosion from starting or spreading.

  • Schedule routine inspections of insulated outdoor systems
  • Repair or replace damaged jacketing and sealants
  • Use moisture-resistant insulation materials
  • Improve drainage to direct water away from equipment
  • Apply protective coatings during seasonal shutdowns or before freezing weather

Working with a professional service provider like Axtell Services gives you confidence that these steps are carried out correctly.

Why Choose Axtell Services

Axtell Services has decades of experience helping Michigan industries manage winter-related corrosion risks. We know how cold weather affects insulated systems and how to protect them.

Our team uses proven coatings, advanced surface prep tools, and proper installation methods tailored to your facility. Whether you need inspection, repair, or full system rehab, we work around your schedule and safety protocols.

Keep your operation running safely and reliably. Contact Axtell Services to schedule a site visit or learn more about our CUI services.

Frequently Asked Questions

What is corrosion under insulation?

It’s a form of corrosion that forms on metal under insulation, often due to trapped water. It weakens steel and causes hidden damage to pipes and tanks.

Why is winter a problem for corrosion under insulation?

Freezing temperatures cause more condensation and can damage insulation, allowing water to reach the metal surface.

Can I tell if CUI is happening without removing insulation?

Only with specialized tools or professional inspection. Surface signs like damp insulation or stains may suggest a problem, but the only way to confirm is to check underneath.

Is corrosion under insulation only found in older facilities?

No, even newer systems can develop corrosion if insulation is damaged, seams are open, or coatings are applied improperly.

What types of coatings protect against corrosion under insulation (CUI)?

Zinc-rich primers, epoxy coatings, and other moisture-blocking systems are common. Selection depends on surface type, environment, and application method.