Choe Hong-Bok, Nishio Yuhei, Kanematsu Manabu
Department of Architecture, Graduate School of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
Department of Architecture, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
Materials (Basel). 2019 Oct 30;12(21):3566. doi: 10.3390/ma12213566.
Hot-dip Galvanized rebar (hereafter, HDG rebar) has an anti-corrosion effect due to the sacrificial anodic reaction of zinc. Additionally, the zinc coating itself provides barrier protection for the steel substrate. Meanwhile, from one of the investigations on the field performance of HDG rebar in concrete, HDG rebar did not protect the substrate when the remaining zinc was under 50 µm. For the evaluation of this property over a short period of time, an acceleration test using impressed anodic current (hereafter, acceleration test) may be useful. This test impresses constant direct current into the rebar and can result in the intended quantitative extent of the anodic reaction. However, in using this test on HDG rebar, it was found that the high rate of applied current density could cause an unintended early end of the anti-corrosion effect of zinc, despite there being more than 50 µm of remaining zinc thickness. In this study, the usability of the acceleration test was investigated to determine if it is a suitable method for evaluating the anti-corrosion behavior of HDG rebar in concrete. As a test variable, a comparatively low rate of applied current density was used in the experiments. As a result, it was clarified that an effective corrosion protection of the substrate was made with an increase of the zinc corrosion amount. This anti-corrosion effect was similar to that known to exist in actual corrosion environments. This behavior was terminated when the concrete cracked, and the substrate became corroded. While the test condition in this study resulted in an early end of the anti-corrosion effect of zinc, a linear correlation was achieved between the applied current density and the remaining zinc thickness at the time that the anti-corrosion effect was terminated. It was found that lowering the applied current density resulted in a more suitable test condition. In conclusion, the acceleration test was found to be useful, although further experimental validation is necessary to confirm this finding.
热浸镀锌钢筋（以下简称HDG钢筋）由于锌的牺牲阳极反应而具有防腐效果。此外，锌涂层本身为钢基体提供了屏障保护。同时，从一项关于HDG钢筋在混凝土中现场性能的调查中发现，当剩余锌层厚度小于50μm时，HDG钢筋无法保护基体。为了在短时间内评估这一性能，使用外加阳极电流的加速试验（以下简称加速试验）可能会有所帮助。该试验将恒定直流电施加到钢筋上，可导致阳极反应达到预期的定量程度。然而，在对HDG钢筋进行该试验时发现，尽管剩余锌层厚度超过50μm，但高施加电流密度可能会导致锌的防腐效果意外提前结束。在本研究中，对加速试验的可用性进行了研究，以确定它是否是评估HDG钢筋在混凝土中防腐行为的合适方法。作为试验变量，在实验中使用了相对较低的施加电流密度。结果表明，随着锌腐蚀量的增加，基体得到了有效的腐蚀保护。这种防腐效果与实际腐蚀环境中已知的效果相似。当混凝土开裂且基体开始腐蚀时，这种行为终止。虽然本研究中的试验条件导致锌的防腐效果提前结束，但在防腐效果终止时，施加电流密度与剩余锌层厚度之间实现了线性相关。发现降低施加电流密度可得到更合适的试验条件。总之，加速试验被认为是有用的，尽管需要进一步的实验验证来证实这一发现。
