Corrosion Under Insulation

Why to focus on Corrosion Under Insulation?

Published 21 August 2019

Corrosion Under Insulation (CUI) is still a major challenge for the process industries. Despite the publication of guidance and standards and often substantial control spend, there continue to be CUI failures, often in late life, many of which are significant in terms of safety, cost and reputation. Your CUI Masterclass trainers and course content providers have direct experience of such failures, how they were managed, why to focus on corrosion under insulation and key lessons learned.



Dr. Clare Watt
Principal CUI/RBI Integrity Engineer
KAEFER Isoliertechnik GmbH & Co. KG.


Dr. Steve Paterson
Corrosion and Integrity Consultant
Arbeadie Consultants Ltd.

The Masterclass provides a good background on CUI prevention, detection, prediction and monitoring and capability today. Advancement in CUI control will rely on a combination of new technologies, collecting and sharing plant data and updating risk assessment methods accordingly.

CUI control measures currently rely on a combination of permanent removal of unnecessary insulation, and, for the remaining insulated equipment, sound insulation and coatings practices with periodic inspection. Inspection is often the only way to prevent failures of carbon steel.

CUI affects both carbon and stainless steels but these different materials need very different control strategies

Industry published guidance indicates that it is possible to prevent most carbon steel CUI failures using a tactical inspection approach

We have direct experience of effective CUI inspection programs but over the past decade an emerging pattern of industry experience demonstrates that this is not easy to achieve:

  • Ineffective CUI inspection programs persisting for many years
  • Resulting in isolated, unexpected critical failures or near-miss failures often in late life
  • Triggering large “catch-up” inspection and maintenance projects (£10-240M/facility depending on size and age
  • Introducing safety concerns for live equipment inspection and maintenance
  • Causing loss of confidence with partners / regulators / insurers and indirect costs which exceed the inspection & maintenance spend
  • Negatively impacting on other critical reliability and maintenance work

Inspection and maintenance planning and prioritisation of CUI commonly involves risk-based assessment methods which can be prone to errors

Different plant processes in different locations will require different CUI solutions from coating and insulation systems to risk based assessment and inspection

Inventories of insulated equipment can exceed 100km piping and hundreds of vessels per asset and even focusing on the highly critical equipment in some climates can still cost £0.3-3M/yr/asset or ~10% of the maintenance budget. We currently spend an estimated 2billion globally on inspection and coating repairs.

  • Factors that influence CUI severity are well known but we are not yet capable of confident CUI prediction and this is not always obvious in all published guidance.
  • There is no published performance data for coating and insulation innovations. It can take 10-20+ years for CUI failure patterns to emerge on plants and hence generate confidence to significantly reduce inspection costs.
  • Reliable inspection of critical equipment is expensive because it requires high coverage, conservative intervals and high reliability of detection. Removing insulation is still the most reliable method.
  • Non-intrusive inspection techniques are constantly improving but as an industry, we have only recently started to evaluate their reliability and cost effectiveness.


Corrosion Under Insulation
15 - 16 Sep 2020 London, United Kingdom