Field Testing of Saline Soil Corrosion of Q235 Steel for Buried Heat Pipelines

The technology of buried heat pipelines has been used more and more because of the demand for the urban construction, environmental protection and energy conservation. Therefore,much attention should be payed to the problem of soil corrosion urgently. In this study, the corrosion behaviors of a typical heat pepeline steel, i.e. Q235 steel were investigated in saline soil containing high concentrations of Cl- at 80 ℃. The results showed that, within 6 months, the corrosion products on the surface of Q235 steel became thickened continually. However, the average corrosion rate first increased and then decreased with the time, the maximum value reached 0.47 mm/a. The corrosion products of Q235 steel reached about 1500 μm after 6 months of the field tests. And the outer layer was composed mainly of Fe3O4, Fe2O3 and SiO2, the inner layer was consisted mostly of Fe3O4. It is suggested that the influence of high temperature, high concentration of Cl- and water brought by the seasonal freezing and thawing resulted in the acceleration of corrosion of the heat pipeline steel buried in saline soil.