Corrosion under insulation (CUI) refers to the external corrosion on the metallic pipe/ equipment
body subjected to thermal insulations. CUI manifests localized corrosion (mainly) and has
always been a driver behind failures on thermally insulated pipelines. Despite the advent of
numerous measures namely protective coatings, and hydrophobic insulations, the issue of CUI
remains an inevitable reality for the pipelines especially those which undergo submerging
conditions from the rainwater in the culverts, being buried under the snow piles, water flooding,
etc. All these moisture intrusion events result in the soaking of insulation thereby exploiting the
CUI risks. This study addresses the ambient temperature CUI behavior of a thermally insulated
carbon steel pipe to mimic the out-of-service (normally happens during maintenance shutdowns,
mothballing, etc.) behavior of thermally carbon steel pipeline(s). The insulated pipe assembly
was submerged under the water for a two day’s period followed by exposure to outdoor
conditions for one year. The insulated assembly was checked for corrosion behaviors using
confocal laser microscopy, and x-ray diffraction; followed by the interpretation of corrosion
modes and kinetics.