The benefits of closed cell, flexible elastomeric foam (FEF) insulation materials have long been appreciated by its users for application in challenging environments, such as marine and offshore. Despite their successful history, it is only recently that efforts have been made to qualify the benefits of FEF systems with respect to mitigating corrosion under insulation (CUI).

The work began in 2014 with an assessment of the long-term performance of damaged insulation systems subjected to a continuous salt water spray environment and temperature conditions conducive to the development and spread of CUI.

This paper describes the details of a second procedure developed by the testing centre INNCOA to assess the performance of several insulation systems with respect to the ingress of water vapour through a damaged section of the covering layer. The insulation systems were subjected to a continuous cycling within the cold/intermediate temperature regime in order to create favourable conditions for water vapour penetration into the insulation system and consequential CUI development.

The results of this evaluation demonstrate that a systems approach to testing better represents real- life conditions for the initiation of CUI caused solely by water vapour ingress. While long term corrosion cannot be prevented, the independent assessment concludes that: ‘Insulation systems operating over a longer period with risk of condensation penetrating the insulation, Flexible Elastomeric Systems are recommended to mitigate corrosion under insulation’.


Corrosion Under Insulation (CUI) is a major issue for oil & gas (both onshore and offshore), chemical process and other related industries. It is estimated that 40-60% of pipe maintenance costs are a result of CUI, and 10% of total annual maintenance costs in these industries is dedicated to repairing damage from CUIi,ii, Severe cases of CUI may put personnel, environment and industry reputation at risk.

”Corrosion under insulation (CUI) refers to the external corrosion of piping and vessels fabricated from carbon manganese, low alloy, and austenitic stainless steel that occurs underneath externally clad or jacketed thermal or acoustic insulation, primary due to the penetration of water”iii

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