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Corrosion under Insulation

How to Prevent it with IPC’s non contact insulation

Corrosion under Insulation

What is CUI?                                             What causes

How to prevent CUI?                                 IPC’s non contact insulation system

Benefits of non contact insulation              Laboratory test scenario

Results                                                       Conclusion


Corrosion under insulation (CUI) is a severe form of localized external corrosion that occurs in carbon and low alloy steel
equipment that has been insulated. This form of corrosion occurs when water is absorbed by or collected in the insulation.
The equipment begins to corrode as it is exposed to water and oxygen.
Corrosion is a natural process, which converts a rened metal to a more stable form, such as its oxide, hydroxide, or sulphide.
It is the gradual destruction of materials (usually metals) by chemical and/or electrochemical reaction with their environment.


Water or liquid ingress into the Insulation system which may cause the insulation materials to soak up liquid, and remain wet.
This is particularly noticeable when:
• Plant operates at temperature range of 12° C to 180° C.
• Bad drainage on the Insulation Cladding System
• Cladding System compromised due to mechanical damage
• Anti-Corrosion Coatings are not up to standard or have been applied incorrectly
• Wet Insulation is in contact with the metal surface
• The corroded surface is mostly hidden by the insulation system and will not be identified until the
insulation is removed for inspection or in the event of metal failure leading to health and safety incidents.

The necessity of protection against corrosion must be determined for each individual plant.



– The correct application of an anti-corrosive coating over equipment.
– The use of low chloride Insulating materials eg. Rockwool.
– Using Pre-formed Sections of Insulating materials
– Installing Drain Plugs for water seepage
– Installing good quality Cladding that meets specications with good sealing practices


And yet, the solution for the avoidance of CUI and the damages and dangers resulting as a consequence, is relatively simple.
The surest method for a prevention of these corrosion processes is the faultless application of a requirement fulfilling anti-corrosive coating and the use of appropriately-formed airlay-spacers, which avoid direct contact of the object surface to be insulated with the humidity-and corrosive-material-enriched insulating material.

These so-called “non contact insulations” prevent the direct contact between the insulating layer and the object surface.
Consequently, the accumulated humidity and corrosive materials within the insulating material cannot result in damage
of the anti-corrosive coating or the surface of the object respectively. Corrosion processes, therefore, cannot even start to begin.
“Non-contact insulations” have been successfully used for some length of time in dierent areas of the oil and gas industries as
well as in rening, for the avoidance and considerable reduction of CUI, respectively. However, up to date, the constructive form
of the air gap between the object surface and the insulating material has been unsatisfactory because the techniques used up until
now often don’t ensure a lasting gap of air, are very work-intensive or even damage the anti-corrosive coating of the object,
which again leads to corrosion under the insulations.
The newly-developed IPC CUI prevention system is the optimal constructive solution for the realisation of
“non contact insulations”.
IPC CUI prevention, with its exactly intertuned system of gap construction and insulation, ideally fullls



The System comprises of:

  1. The use of high performance, low chloride, pre-formed Rockwool Insulation
  2. The addition of an Insulation Spacer, used to create an air gap between the insulation and the equipment. The spacer is
    installed at 300mm intervals along a vertical or horizontal pipe.
  3. The addition of drain plugs along the length of the insulated equipment to dispel moisture.

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