Corrosion Under Insulation (CUI) is widely acknowledged to be a critical issue facing plant operators in the oil, gas and chemical industries. CUI studies from a petrochemical facility have shown that 40-60% of pipe maintenance costs are due to CUI and approximately 10% of the total maintenance budget is spent repairing damage from CUI, mainly on pipes. The risk of corrosion under insulation is considered high in the temperature range 50 – 175°C (122 ߝ 347°F) and extreme when in cyclic temperature service between −20 and 320°C (−4 – 608°F).

If CUI is not found in time, then the consequences can be severe for personnel, the environment and company reputation.

This paper will review the current test methods used for determining the suitability of coatings to prevent corrosion under insulation when the insulation, inevitably, gets wet. We will introduce a new, small scale, method for testing coatings using the parameters adopted in ASTM G189-07 (cyclic testing wet 60°C (140°F) and dry at 150°C (302°F) and Classification CUI-2 within ISO 19277 that can rapidly screen the suitability of a coating to withstand the test conditions.

We will show how the use of embedded sensors in the coating can be used to accurately determine the temperature, the amount of water in the coating and the barrier properties of the coating during the whole test cycle. Failures such as delamination, blistering, cracking or corrosion can be distinguished easily and onset of failure can be accurately determined.


Corrosion under Insulation (CUI) costs industry millions of dollars. Water ingress into conventional insulation systems can result in accelerated corrosion of the steel substrate which, if unchecked, will result in structural failure of the vessel or pipe. If the structure is operating under high pressure then this failure would be catastrophic. CUI can result in significant loss of revenue from downtime, maintenance and replacement of corroded structures.

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