Corrosion and its inhibition in SA213-T22 TIG weldments used in power plants under neutral and alkaline environments

Failures of industrial boilers have been reported to be mainly due to water side corrosion and scaling. Boiler corrosion is due to highly alkaline or acidic conditions of the boiler water. The present work has been aimed at investigating the corrosion behaviour of T22 (2.25 Cr–1 Mo) boiler steel TIG weldments in neutral and alkaline media. The parent metal and weld root regions are chosen as regions of exposure for the study made at room temperature and at 100 °C. Electrochemical polarization technique such as Tafel line extrapolation (Tafel) was used to measure the corrosion current. Corrosion inhibition using thiourea at 100 ppm concentration was studied in these experiments. Micro-structural observation and surface characterization using SEM and XRD studies have been made on samples exposed at 100 °C. The results show that parent metal experiences higher corrosion rate than weld metal and thiourea as inhibitor is found unsuitable in NaOH medium.