Product Profile: Fighting Against Corrosion Under Insulation


By Simon Daly, Hempel A/S


Corrosion under insulation (CUI) is an often unseen and costly hazard for operators in the chemical processing industries. Left to develop, it can be catastrophic. 

CUI occurs when moisture becomes trapped between insulating materials and the pipework, ductwork, valves and other external equipment vital to the operation of refineries, petrochemical plants and other processing and storage facilities. Not resolving a CUI problem can lead to unscheduled shutdowns, which can affect an operator’s bottom line, and it can damage reputations – particularly if supply chains are disrupted. More importantly, if undetected, CUI can also have an impact on safety, so it is vital that the proper preventive measures are taken.

Prevention is the Best Form of Defense

Understanding CUI and recognizing the trigger factors is key to reducing the chances of CUI developing. If the right choices are made at the outset — selecting the correct insulation materials, optimizing construction and design, choosing the right protective coating — CUI may even be avoided altogether. 

Three existing coating systems that are generally used to guard against CUI are epoxy/epoxy phenolic, thin film silicones and zinc silicates. Epoxy/epoxy phenolic coating offers excellent performance when operating in the CUI temperature range, but when process excursions exceed that range, the coating is likely to crack, and subsequent corrosion might occur.

Thin film silicone paints based on silicone resins are ideally suited to the hot and dry conditions experienced during process cycling, but outside of those conditions, corrosion protection becomes extremely limited. 

Zinc silicate paint can resist reasonable temperatures (typically up to 400 degrees Celsius/752 degrees Fahrenheit), but due to its sacrificial nature, rapid degradation will occur when the paint is exposed to hot, wet CUI environments.  

An alternative to these systems, Versiline CUI 56990 provides corrosion protection across a wide range of conditions. Based on fiber-reinforced, single-component, inert modified inorganic copolymer technology, the system has demonstrated a unique resistance to micro-cracking at elevated temperatures, according to manufacturer Hempel. The company says that the coating will protect against corrosion even when operating temperatures change during processing or infrequent cycling.

Resistance against this range of temperatures — from -196C 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. This level of flexibility and performance in one product can simplify the specification process and reduce the frequency of maintenance.

Key Decisions from the Outset

CUI can lead to serious problems for operators. Making smart choices from the beginning can minimize any potential loss of revenue due to down time required for maintenance and remedial work. By choosing the right coating solution, critical equipment will be protected. 

Versiline CUI 56990 at a glance
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.

Simon Daly, Hempel A/S

Simon Daly is the group oil and gas market segment manager for HEMPEL A/S. With 28 years of coatings experience in laboratory, technical, sales and marketing positions — mainly servicing the oil and gas industry — he is currently responsible for oil, gas and thermal power strategy. See his bio on LinkedIn.