Experimental investigation on corrosion behavior of slag-cement-mortar-lined ductile iron pipe in flowing solutions

Abstract

In this study, a series of experiments were performed to electrochemically and microscopically investigate the corrosion behavior of slag-cement-mortar-lined ductile iron (SCMLDI) pipes in flowing solutions. Firstly, some ductile iron (DI) pipe specimens lined with slag-cement mortar (SCM) were prepared. Secondly, the accelerated corrosion behavior of specimens in flowing pure water, 6M solutions of NH4NO3 and NH4Cl were studied by electrochemical measurement, such as Tafel polarization (TP) and EIS. Then, their microscopic morphology, phase composition and chemical valence state of the SCM lining and DI surface were characterized by SEM/EDS, XRD and XPS. Results show that, during the 120-day immersion, the specimen in pure water has basically no leaching of SCM lining and corrosion of DI surface, but in 6M NH4NO3 solution, there produces an obvious leaching of SCM lining and no corrosion of DI surface. However, there produce a severe leaching of SCM lining and a high corrosion of DI surface of the specimen in NH4Cl solution.