Corrosion under insulation (CUI) refers to the degradation of metals under thermal insulation which reportedly manifests as localized corrosion and pitting. To simulate the corrosion behavior of various insulation materials, the ASTM standard for the laboratory simulation of CUI (i.e., ASTM G189-07, Standard Guide for Laboratory Simulation of Corrosion Under Insulation) and leachate corrosivity (i.e., ASTM C1617, Standard Test Method for Quantitative Accelerated Laboratory Evaluation of Extraction Solutions Containing Ions Leached from Thermal Insulation on Aqueous Corrosion of Carbon Steel) propose procedures for mimicking the corrosion behavior of insulations. However, the CUI rate may be influenced by the aging of insulation from heating when installed on pipes. There have been reported studies that address the implications of long-term heating on the chemical properties of insulation(s). To account for the effects of aging on CUI rates, this work compares the CUI behavior of pristine and short-term aged insulation materials (via aging under laboratory settings). This research work addresses the corrosion behavior of three different insulation materials namely fibrous mineral wool, calcium silicate, and pearlite in pristine and short-term aged conditions. The candidate insulations were tested for corrosion behavior using ASTM G189-07, whereas the leachate extracts from the candidate insulations were characterized for corrosion rates using ASTM C1617 test method, respectively. The corroded steel samples from each test method (i.e., ASTM G189 and ASTM C1617) and candidate insulations were visually inspected, followed by 3D confocal laser topography and scanning electron microscopy to understand the corrosion modes and evaluate the effectiveness of the test methods. The ASTM C1617 test method showed overall shallow pits than the ASTM G189 test method pits. However, the impacts of thermal degradation of insulations on CUI rates during the short duration ASTM G189 and ASTM C1617 tests were not pronounced.