Investigation of temperature effect on the corrosion behavior of carbon steel in contact with rock wool thermal insulation

In this research, the corrosion of API 5L 42X steel in contact with rock wool thermal insulation at four temperatures 20, 40, 60 and 80°C is investigated. For this purpose, the tafel polarization, cyclic polarization and weight loss examinations were used. Electrochemical and weight loss tests were conducted in insulation’s leachate and in contact with wet insulation, respectively. Furthermore, in order to confirm of corrosion tests results, the corrosion products that obtained from weight loss measurements at 20 and 80°C, were evaluated by X-ray diffraction (XRD) analysis. The results of tafel and weight loss examinations for 20°C showed that rock wool insulation alone had little talent in the corrosion creation on steel samples, which this outcome of the alkaline nature of it’s leachate and low chloride ion concentration in this insulation. In weight loss measurements due to formation of a close system, by the increase of temperature from 20 to 80°C, the corrosion rate continuously was increased, while such behavior because of formation of an open system was not observed for tafel tests in the temperature range of 60 to 80 ° C. Cyclic polarization tests and microscopic observations of samples surface after weight loss measurements have shown that the increasing of temperature is increased the tendency to localized corrosion.