From hidden risk to measurable insight: advancing how the industry tackles corrosion under insulation
Corrosion under insulation (CUI) remains one of the most persistent and complex integrity challenges facing the oil, gas, petrochemical and associated industries. Despite decades of progress, it continues to drive asset degradation due to the interaction of moisture, insulation systems and cyclic temperatures. The challenge lies not only in prevention but in understanding how coatings perform under real service conditions.
The hidden nature of CUI makes it particularly difficult to manage. Moisture ingress beneath insulation creates localized corrosion cells, often progressing undetected until failure occurs. Addressing this requires a system-level understanding across coatings, insulation and operating environments. End users still rely heavily on costly intrusive inspection methods, frequently requiring insulation removal to identify CUI.
Linking testing to standards and real-world performance
Coating test standard ISO 19277:2018, Petroleum, petrochemical and natural gas industries — Qualification testing and acceptance criteria for protective coating systems under insulation, provides a recognised framework for evaluating coating performance under cyclic corrosion under insulation (CUI) conditions. AMPP TM21442:2023, Test Method for Evaluation of Protective Coatings for Use Under Insulation, is a more recent industry-recognised addition to support coating evaluations. This later test provides a structured programme of cyclic thermal and corrosion exposures options, and provides additional performance data to support the assessment of coatings under differing CUI conditions.
However, translating laboratory results into reliable field predictions remains a significant challenge. To address this, an industry working group has been collaborating since 2023 through the InnovateCUI Joint Industry Project, led by Sirris, a Belgian non-profit research and innovation centre for the technology industry. The project brings together major asset owners, coating manufacturers, and sensor providers in a collaborative effort to advance the understanding and mitigation of CUI. Participating asset owners included Shell, Equinor, BP, Chevron, SABIC, Dow, and Gassco.
CUI “short” duration test method development. © Sirris
From compliance to Performance Insight
An ambition of the work undertaken has been to validate whether laboratory testing of coating technology performance is representative for failures observed in the field. Correlations between test methodologies, both short-duration (approximately four months) and long-duration (approximately 18 months) testing programs, were employed. The long-duration testing was conducted to try and closely replicate coating degradation under real-world service conditions, while the short-duration testing was used to determine whether it could reliably predict and follow the performance trends observed in the longer-term exposures.
Coating formulation plays a critical role in determining in-service performance. While some end users still refer to AMPP SP0198-2017, Control of Corrosion under Thermal Insulation and Fireproofing Materials for baseline selection criteria, this standard does not fully capture the influence of formulation-specific variables of modern coatings. Differences in resin and binder chemistry, as well as pigment composition, can significantly affect moisture resistance, adhesion, and long-term durability under cyclic conditions of coatings. These factors and testing are not explicitly addressed within SP0198:2017 currently.
"One of the key challenges in CUI management is not simply testing coatings, but ensuring that test methods can meaningfully differentiate performance. By benchmarking technologies with known field histories, we can validate whether laboratory methods truly reflect real-world behavior and give operators greater confidence in their coating selection."
Doug Beaumont, Technical Specialist - Anticorrosive and Finishes, AkzoNobel.
Image left: Interbond 2340UPC demonstrated strong performance through long and short-duration test programs
"The main objective of the InnovateCUI project has been to work on developing improved test methods and simultaneously improve our understanding of CUI coating degradation in a collaborative spirit. The project has made clear that it is important not only to focus on pass/fail criteria, but also to study degradation over time in a long-duration test. As such, differences in degradation mechanisms between different coatings can be elucidated. It is critical to understand how the exposure conditions in the test influence the degradation. This and other aspects we will continue to explore in Phase 2 of the project that is currently starting up." Jeroen Tacq, Senior Engineer Metals, Sirris
Towards predictive and integrated asset integrity
The group, further investigated the integration of CUI monitoring sensor technologies. This work aimed to support the industry's transition towards predictive maintenance, helping operators optimise maintenance strategies, improve safety and environmental.
"Customers do not experience CUI as a coatings issue alone; they experience it as an asset integrity challenge. Through initiatives such as the InnovateCUI Joint Industry Project, we are working to better understand how coatings, inspection technologies, and monitoring solutions can be integrated to improve CUI management and reduce overall lifecycle costs. Our customers expect both reliable coating performance and a holistic approach to asset integrity, and our focus is on supporting both."
Toby Stein, Subsegment Manager Downstream, AkzoNobel.
Through collaboration, closer alignment with industry standards, and a stronger focus on performance-based assessment, the industry is transforming CUI from a hidden risk into a measurable and manageable challenge. International Paint's approach remains focused on understanding coating performance across technologies and enabling integration within the broader asset integrity systems of the future, while recognising that the primary function of these systems is to support what remains the first line of defence against CUI: reliable and robust CUI prevention coatings.
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