Differences in Gel Coating Technology for Corrosion Under Insulation Applications

Corrosion under insulation (CUI) of steel operating equipment and piping is recognized as an important problem in the ammonia refrigeration, chilled water, chemical and petroleum industries. A systems approach to CUI includes the correct material selection and design of the jacketing, insulation and coating. This approach will help prevent CUI, but many corrosion engineers would agree that electrolytes will eventually find their way into even the best system. Selecting the right coating is extremely important, as the coating is the last line of defense for keeping the electrolyte from the metal surface and preventing corrosion.

Historically, many different types of products have been used to prevent CUI. One of the most common is the use of a synthetic fabric impregnated with petroleum jelly that is spiral wrapped around bare piping prior to the installation of the insulation. Known as “grease tapes,” these products do not typically offer long-term performance and can add to the overall insulation system cost by requiring insulation with a larger inside diameter to cover the tape. These tapes are inexpensive and fairly easy to apply, but do not provide long-term performance.