Corrosion under insulation (CUI) is one of the problems crippling the gas and oil industry. It can cost companies a lot of money every year in repair, inspections, and replacement costs. It refers to a form of corrosion that occurs between the material used for insulating gas lines and the outer surface of a pipeline. corrosion under insulation is the cause of most leaks experienced in the oil and gas industry. It is also one of the problems that companies in the gas and oil industry are struggling to address. Water will always seep into the insulating materials and eventually damage the inner and outer surface of the pipeline.