When Problems Lurk Beneath the Surface


By J. Oriol Ossó, Hempel A/S

getty images / jevtic 

Often, the most corrosive threat is that which is unseen. Slowly festering beneath the surface, corrosion under insulation (CUI) is a pervasive and insidious threat to any structural asset and must be taken seriously. CUI occurs when moisture becomes trapped between insulating materials and the pipework, ductwork, valves and other key external equipment vital to the operation of refineries, petrochemical plants and other processing and storage facilities.

It is the root cause of a wide range of mechanical, structural and safety problems across the chemical and processing industries yet is often sidelined in maintenance schedules and budgets precisely because CUI is inherently difficult to detect. (Out of sight and out of mind.) However, if left unaddressed for too long, CUI will inevitably manifest itself, and it often results in dangerous, costly and irreversible damage to assets and the businesses that rely upon them.

It seems obvious then, that the best solution for managing this threat is to work with an experienced coatings manufacturer that understands the hidden dangers caused by CUI, use quality protective coatings from the outset and closely observe the asset over time.

Looking for Vulnerabilities

There are some common culprits when it comes to coating failures that lead to CUI: Poor application, application of an incorrectly specified product and, more rarely, a defective product itself. Making sure the exact specified products (there is no single-product solution) are applied to each constituent part of the asset, each different material and each operating environment is critical. This is why it is so important that asset owners and operators work closely with their coatings manufacturer and supplier to determine a coatings solution tailored to their precise needs.

Assessing the temperature influences on the coating is a critical consideration. CUI is widely described as occurring in the temperature range of 50 -175 C, although in the case of environments with high relative humidity – the so-called “sweating” pipe syndrome – corrosion beneath insulation can occur below this temperature. Coatings respond very differently to temperature, and as such must be carefully considered and tested in formulating a coatings solution for each unique asset.

Compatibility Testing

There are several testing procedures followed for determining a coating’s response to a range of temperature environments and, therefore, its effectiveness for guarding against CUI. These tests are varied but can be broadly split into three categories:

  1. Tests that can be used to characterize the material and its behavior under thermal conditions;
  2. Tests that indicate the performance of the coating material when exposed to a real or simulated CUI environment; and
  3. Tests that could reasonably be needed to determine a coating’s suitability for multiple uses — for example, a coating for insulated and uninsulated environments.

From these testing procedures, decision makers can begin to determine the coating specification required and work with engineers to ensure that coatings are applied in the right environments, at the right time and to the highest standard.

A More Flexible Solution

While there are variations in the coatings available for CUI protection, there are three key systems that are most commonly used to guard against CUI: epoxy/epoxy phenolic, thin film silicones and zinc silicates. When asked to recommend a paint solution that prevents and combats CUI, experts at Hempel frequently recommend the company’s Versiline CUI 56990. They note that, based on fiber-reinforced, single-component, inert modified inorganic copolymer technology, this solution has demonstrated excellent resistance to CUI and to micro-cracking at elevated temperatures, requiring less maintenance.

Designed to provide corrosion protection across a wide range of conditions, it offers specification simplicity, which is an important consideration when developing complex assets and infrastructure. Resistance against a broad range of operating temperatures (-196 C to 650 C) makes this particular coating suitable for almost all oil, gas and petrochemical processing and storage facilities, including offshore floating facilities and assets in harsh environments. Delivering operators this kind of flexibility in a single product ensures that there will be no dormant corrosion threats waiting to strike.

Wide range of heat resistance — from -196 C to 650 C — providing operators more flexibility with a single product
Built on fiber-reinforced, single-component, inert modified inorganic copolymer technology, exhibiting a unique resistance to micro-cracking, minimizing maintenance
Complies with NACE SP0198: 2017 categories SS-5, CS-6 and CS-8
Extensively tested, both by Hempel and an independent test house, offering proven performance

Claims or positions expressed by sponsoring authors do not necessarily reflect the views of TPC, PaintSquare or its editors.


J. Oriol Ossó, Hempel A/S

J. Oriol Ossó is head of Energy, responsible for the global energy product portfolio at Hempel A/S. He holds a Ph.D. in material sciences, obtained from his work with Max Planck in metals research and the Autonomous University of Barcelona. Ossó has over 12 years of experience in the chemical and coatings industry, having previously worked for international companies BASF and Air Products.




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