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.
This paper is an endeavor to investigate an insulated mild steel pipe that exposed to three sea water drops rate (10, 30, and 50 drops/minute) at room temperature. Various experimental strategies were employed including visual inspection; scanning electron microscopy (SEM) with EDAX. After removing the insulation material, it was observed that pipes were corroded. However, the extent of corrosion was varied which was attributed to the drop rates, it was revealed that corrosion process was initiated due to water and ions penetration through the insulation, such revelation highlighted the necessity to properly examine the pipe and the insulating material. Results also revealed that severity of corrosion is proportional to the drops rates. EDAX analysis of the pipe surface and the insulating material shows the presence of difference ions including Na+, Cl-, Mg2+, Si2+ and others, the results highlighted the importance of material selection and the necessity for early detection strategy in order to avoid catastrophic failure.
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