Severity of corrosion under insulation (CUI) to structures and strategies to detect it

Abstract This review paper considers the research conducted in the past 30 years in the field of corrosion under insulation (CUI). CUI is a significant challenge in many industries for reasons of high cost and risk because it proceeds undetected under insulation. CUI is an unavoidable problem which may potentially cause personnel injury or even fatalities. Presently, CUI counts for as much as 40 to 60% of pipeline-repairing cost. The use of coating under the insulation has been shown very efficient in the mitigation of CUI. Moisture and ion penetration, particularly chlorides, through the insulation and coating may produce stress corrosion cracking of austenitic stainless steels. The process of applying insulating materials on metal surfaces and the precautions that need to be taken are explained. Beside visual inspection, techniques such as neutron backscatter, capacitive imaging and pulsed eddy current can be used to detect the presence of CUI. The strength and limitations of the available commercial detection techniques are evaluated. A comprehensive list of industrial standards dealing with CUI is provided.