Experimental Assessment on Corrosion under Insulation (CUI)

Corrosion under insulation (CUI) is a great concern to the petroleum, gas and
chemical processing plant. Due to nature of the corrosion is hidden beneath the
insulation, the detection by conventional non destructive test methods is unreliable.
Current practice to maintain the reliability of in plant equipments is through the
implementation of Risk Based Inspection (RBI). However, the scarcity data of CUI
causes difficulties in Risk Based Inspection (RBI) analysis. The objective of the
project is to generate experimental data representing CUI in the marine environment,
following the guidelines in API 581. The test will be based on the newly published
ASTM G189-07 Standard Guide for Laboratory Simulation of Corrosion under
insulation The CUI test cell is fabricated based on ASTM Gl89-07 and experiments
were conducted using two different techniques, which are Linear Polarization
Resistance (LPR) and Weight Loss methods. Several experiments have been
conducted to measure the corrosion rate at different temperatures from 60, 70, 80,
and 90 Celsius. For the test at 60°C and 70°C , both LPR and weight loss methods
resulted in the average corrosion rate of O.l8mm/yr as compared to the API 58,
where the corrosion rate is O.l3mm/yr. However, for test at 80°C and 90°C, the
experimental results are in good agreement with data in the API 58. In conclusion,
experimental assessment of corrosion under insulation based on ASTM Gl89-07
produced good agreement with the data published in API 581.