Effect of temperature and time of wetness on corrosion of carbon steel under insulation

This study was carried out to clarify the effect of temperature and time of wetness on corrosion of carbon steel under insulation. The specimen used was carbon steel SS400. In this test, the specimen was covered with calcium silicate insulation and heated in a temperature range from 40 to 200°C by an electric heater. Corrosion test was conducted by pouring deionized water of 25 to 50 ml into the insulation. The time of wetness on the steel surface under the insulation was evaluated using the ACM sensor. The results of the corrosion test showed that corrosion was not found at temperatures above 100°C. On the other hand, corrosion occurred locally at temperatures between 40 ∼ 90°C and the corrosion depth became deeper with decreasing steel surface temperature. The time of wetness of the steel surface measured with the ACM sensor increased with decreasing steel surface temperature. This indicates that the increase in time of wetness on the steel surface has more significant effect on corrosion of the steel under insulation than the increase in the corrosion reactivity with increasing temperature.