School of Environmental Science and Engineering, Tianjin University, Tianjin 300350, China; Advanced Water Management Centre, The University of Queensland, St. Lucia, QLD 4072, Australia.
Sustainable Minerals Institute, Julius Kruttschnitt Mineral Research Centre, The University of Queensland, Indooroopilly, QLD 4068, Australia.
Sci Total Environ. 2019 Feb 1;649:739-748. doi: 10.1016/j.scitotenv.2018.08.362. Epub 2018 Aug 27.
Hydrogen sulfide is a controlling factor for concrete corrosion in sewers, although its impact on sewer rebar corrosion has not been investigated to date. This study determined the corrosion mechanism of rebar in sewers by elucidating the roles of chloride ions, apart from the effects of hydrogen sulfide and biogenic sulfuric acid. The nature and distribution of rusts at the steel/concrete interface were delineated using the advanced mineral analytical techniques, including mineral liberation analysis and micro X-ray diffraction which is the first-ever use in such studies. The corrosion products were found to be mainly iron oxides or oxy-hydroxides. HS and biogenic sulfuric acid did not directly participate in the product formation of steel partly covered by concrete or directly exposed to sewer atmosphere. Instead, chloride ions played an important role in initiating steel corrosion in sewers, supported by a thin chloride-enriched layer at the steel/rust interface. Away from the chloride-enriched layer, iron oxides accumulated on both sides of the mill-scale to form a corrosion layer and corrosion-filled paste respectively. The corrosion layer around rebar circumference was non-uniform and the rust thickness with respect to polar coordinates followed a Gaussian model. These findings support predictions of sewer service lifetime and developments of corrosion prevention strategies.
硫化氢是污水管道中混凝土腐蚀的控制因素，尽管迄今为止尚未研究其对污水管道中钢筋腐蚀的影响。本研究通过阐明氯离子的作用，除了硫化氢和生物硫酸的影响，确定了污水管道中钢筋的腐蚀机理。使用先进的矿物分析技术，包括矿物解离分析和微 X 射线衍射，首次在这类研究中使用，描绘了钢/混凝土界面处铁锈的性质和分布。腐蚀产物主要为氧化铁或氧氢氧化物。HS 和生物硫酸并没有直接参与部分被混凝土覆盖或直接暴露于污水气氛中的钢筋的产物形成。相反，氯离子在启动污水管道中的钢筋腐蚀中起着重要作用，这得到了在钢/铁锈界面处存在薄的富含氯离子层的支持。远离富含氯离子层，氧化铁在轧钢厂两侧积累，分别形成腐蚀层和腐蚀填充膏。钢筋周围的腐蚀层不均匀，相对于极坐标的锈层厚度遵循高斯模型。这些发现支持对污水管道使用寿命的预测和腐蚀防护策略的发展。
