Evaluation of Effect Of Operating Temperature To Corrosion under Insulation (CUI)

Corrosion under insulation (CUI) is a major common problem shared by all of the refining, power, industrial, petrochemical, onshore and offshore industries on a worldwide scale. CUI is a form of localized external corrosion that occurs in carbon manganese, low alloy, and austenitic stainless steel piping and vessels that occurs underneath externally clad /jacketed insulation due to the penetration of water[1]. The majority of CUI occurrences reported are between the -4°C and 175°C (25°F and 347°F). This research is done to study the relationship between operating temperature and corrosion rate due to CUI. A laboratory cell was setup according to ASTM G189-07 for the simulation of CUI. The CUI cell consisted of six carbon steel ring specimens separated by insulated spacers and held together by blind flanged pipe sections on both ends. Thermal insulation which was placed around the testing section provided the annular space to retain the solution which represents the test environment. The ring specimens were used to test electrodes in two separate electrochemical cells. Corrosion measurements were made using both electrochemical polarization resistances and mass loss data under isothermal test conditions. The corrosion rate at higher operating temperature (121°C) was found to be higher compared to corrosion rate at lower operating temperature (65°C).