Corrosion under insulation happened when water came into thermal insulation layer.The pH value, conductivity andions contentsof aqueous extracts of glass wool,141b system polyurethane foam and silica aerogel insulation blanketsanddeionized waterwere tested to estimate their corrosivity and provide references for thermal insulation materials selection and corrosion control.The results showed thatthe lixivium of glass wool was alkalescent. Its conductivity was the largest among the three and increased with the soaking duration and temperature rising.It containedCa2+, CO32-, SO42-and Cl-, which easily caused pitting corrosion and external stress corrosion cracking.The lixivium of141b system polyurethane foam wasalkalescent, the pH value of which decreased with the soaking duration and temperature rising. The conductivity was relatively smaller and that of 80℃ lixivium was larger than lixivium under room temperature.SO42-and CO32-weren’t detected in thelixivium.The lixivium ofsilica aerogel insulation blankets was neutral and changed into acid with soaking duration and temperature increasing.The conductivity changed slightly with soaking duration and temperature variation.SO42-and CO32-weren’t detected either.Compared with thedeionized water, theconcentrationofCl-inlixivium of141b system polyurethane foam and silica aerogel insulation blankets was closed to0 mg/L.