Corrosion Under Insulation (CUI) remains one of the most underestimated risks in industrial environments. It develops out of sight, beneath insulation systems that are intended to protect assets but can, under the wrong conditions, accelerate degradation instead. The result is often discovered only after failure — when a leak occurs, a fire risk emerges, or operations are forced to shut down unexpectedly.
For industries such as refining, mining, chemical processing, and critical infrastructure, CUI is not simply a maintenance concern. It is a serious operational and safety risk with the potential to impact personnel, production, and long-term asset integrity.
At Dragon Jacket Insulation, we set out to design and engineer an industrial insulation system that would eliminate (or at least drastically reduce) the risk of CUI, and the result is an insulation system that resists and repels water and moisture from reaching protected pipes and fittings through decades of use.
What Is Corrosion Under Insulation (CUI)?
CUI refers to the corrosion of metal surfaces — typically piping, tanks, or pressure vessels — that occurs beneath insulation. Because insulation systems conceal the underlying metal fittings, corrosion can progress for extended periods without detection.
This form of corrosion is particularly problematic because it does not present obvious external indicators. Unlike exposed corrosion, which can be identified through visual inspection, CUI often advances until the material has significantly weakened. By the time it is discovered, the system may already be close to failure.
CUI most commonly affects carbon steel and low-alloy steel assets, especially those operating in temperature ranges where moisture can accumulate and persist.
Why CUI Presents a Serious Risk
The primary danger of CUI lies in its hidden nature. When corrosion develops unnoticed, it compromises the structural integrity of critical systems without warning. This can lead to sudden and severe consequences.
Failures caused by CUI are not gradual; they are often abrupt and sometimes catastrophic. A pipe wall weakened by corrosion may rupture under pressure, releasing hazardous or high-temperature materials. In refining environments, this can escalate into fire or explosion risks. In other industrial settings, it can result in equipment damage, environmental release, or injury to personnel.
The operational impact is equally significant. Unplanned shutdowns caused by CUI-related failures disrupt production schedules, strain maintenance resources, and can lead to extended downtime while systems are inspected and repaired.
How CUI Develops
CUI occurs when moisture comes into prolonged contact with metal surfaces beneath insulation. This moisture may originate from external sources such as rain or washdowns, or from internal condensation within the system.
Temperature plays a critical role. Systems operating in moderate or cyclical temperature ranges — where water can repeatedly condense and evaporate — are especially vulnerable. These conditions create an environment where corrosion reactions can accelerate over time.
The design and condition of the insulation system itself also contribute. Traditional insulation materials can absorb and retain water, allowing moisture to remain in contact with a metal surface. Over time, insulation may degrade, creating gaps or pathways that allow additional water ingress.
Installation quality further influences risk. In field-applied insulation systems, inconsistencies such as poor sealing, gaps at joints, or uneven coverage can allow moisture to penetrate and become trapped. Once inside, it is often difficult for the system to dry out, sustaining and preserving the corrosive environment.
Documented Incidents and Real-World Impact
CUI has been identified as a contributing factor in numerous industrial failures, some with significant economic and safety consequences.
One of the most widely referenced cases occurred in Alaska in 2006, when corrosion under insulation led to severe wall thinning in an oil pipeline. The resulting rupture caused a spill of more than 200,000 gallons of crude oil, triggering environmental damage, regulatory action, and costly operational disruption. The incident highlighted how undetected corrosion can escalate into large-scale failure.
In refining and chemical processing facilities, investigations by regulatory bodies such as the U.S. Chemical Safety Board have linked CUI to multiple hydrocarbon release events. In several cases, corroded piping failed unexpectedly, releasing flammable materials that ignited and caused fires. These incidents not only damaged infrastructure but also placed personnel at risk and required emergency shutdowns.
CUI has also been associated with high-pressure steam line failures in power generation and industrial plants. When these systems rupture, they can release energy and materials capable of causing severe injury or damage. Similarly, storage tanks affected by CUI have experienced leaks that required extensive cleanup and remediation efforts.
Economic Consequences of CUI
The financial impact of CUI extends well beyond the immediate cost of repair. When a failure occurs, organizations must address both direct and indirect costs.
Direct costs typically include equipment replacement, emergency repairs, environmental cleanup, and potential regulatory penalties. However, indirect costs often exceed these initial expenses. Lost production during unplanned downtime, increased inspection requirements, and shortened asset lifespans all contribute to the total economic burden. While general liability insurance can cover some of the costs, insurance cannot remedy personal injuries, lost productivity, and reputational harm.
Across industries, preventing corrosion-related damage accounts for a substantial share of maintenance and capital expenditures. Due to its hidden and progressive nature, CUI concerns represent a significant portion of these costs.
Why Traditional Insulation Systems Fall Short
Many conventional insulation systems were not designed with long-term moisture resistance as a primary consideration; instead, they focus on insulation value. However, over time, these systems are susceptible to water ingress and retention, which not only degrades insulation value, but introduces CUI issues.
Multi-layer systems with numerous seams and penetrations increase the likelihood of water entry. In some cases, external jacketing may trap moisture inside the system, preventing it from drying. Materials that absorb moisture create sustained contact between water and metal surfaces. In large and complex systems, these problems make it difficult to prevent or detect CUI using traditional approaches.
Reducing the Risk of CUI
Addressing CUI requires a shift toward insulation systems and practices that prioritize moisture management, durability, and ease of access. Effective strategies include:
- Selecting insulation materials that resist water absorption
- Designing systems with minimal seams and entry points
- Ensuring consistent, high-quality installation
- Prioritizing reusability for inspection and maintenance purposes
Prefabricated insulation systems such as those offered by DJI have distinct advantages in this context. DJI provides engineered insulation components with controlled fit and reduced variability. By limiting opportunities for moisture ingress and maintaining consistent performance, DJI’s systems help mitigate one of the primary drivers of CUI.
DJI: Enhancing Inspection and Prevention
Even with improved insulation systems, proactive inspection remains essential. Facilities often implement risk-based inspection programs to identify high-risk areas and prioritize monitoring efforts.
Dragon Jacket’s improved insulation design allows easy inspection that does not destroy either the structural integrity or the R-value of insulation. Each segment of DJI is a rigid, polyurea-coated clamshell that can be removed and replaced without specialized training or tools. Scheduled inspections that allow for early detection of potential issues are easily and swiftly accomplished. This preventative maintenance step, combined with DJI’s improved insulation design, provides a more comprehensive approach to managing CUI risk.
Understanding how CUI develops — and learning from documented failures — underscores the importance of using an insulation system designed to resist moisture, maintain integrity, and support long-term reliability.If you are concerned about CUI risk in your facility, Dragon Jacket Insulation provides a prefabricated insulation solution engineered to reduce moisture intrusion, improve durability, and support safer, more predictable operations. To learn more, obtain a quote, or schedule a demonstration, contact Dragon Jacket Insulation.
