Steel rebar's corrosion greatly affects the durability of reinforced concrete (RC) structures. Recently, enamel coatings have been developed for steel rebar's corrosion protection. Given that the anticorrosion performance of enamel coatings is strongly related to their microstructure, in this study, pure enamel coating (PE) and three silicon carbide/enamel composite coatings with 2.5, 5, and 7.5 wt% silicon carbide addition (S2.5, S5, and S7.5) were prepared on low-carbon steel rebars, representing four different microstructure states, which are severely cracked with porosity of 6%, partially cracked with porosity of 17%, slightly cracked with porosity of 20%, and uncracked with porosity of 26%. The long-term corrosion behavior of different coated rebars was investigated by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, neutral salt-spray test, and morphological observation to understand the effect of silicon carbide content and coating microstructure on the corrosion behavior. Long-term electrochemical studies (210 days) showed that the R_por and R_ct of S7.5 remained 12 times and 5 times that of PE, respectively, indicating an improved corrosion protection with silicon carbide addition. Combined corrosion studies and microstructure results revealed that the corrosion behavior of enamel coated rebars was closely related to the coating microstructure, especially the pores and microcracks. Furthermore, the competitive mechanism of electrolyte penetration degeneration and “self-healing” like enhancement was proposed to interpret the corrosion evolution modes of different coated rebars. The findings of this work give a deep understanding of the corrosion behavior of silicon carbide/enamel composite coatings and provide a solution for long-life RC structures.

钢筋的腐蚀极大地影响钢筋混凝土 (RC) 结构的耐久性。最近，已开发出用于钢筋腐蚀保护的搪瓷涂层。鉴于搪瓷涂层的防腐性能与其微观结构密切相关，在本研究中，纯搪瓷涂层 (PE) 和添加了 2.5、5 和 7.5 wt%碳化硅的三种碳化硅/搪瓷复合涂层（S2.5，S5、S7.5）在低碳钢筋上制备，代表四种不同的显微组织状态，严重开裂气孔率为6%，部分开裂气孔率为17%，轻微开裂气孔率为20%，未开裂孔隙率为 26%。不同涂层钢筋的长期腐蚀行为通过开路电位（OCP）、电化学阻抗谱（EIS）、动电位极化、中性盐雾试验和形貌观察等方法研究碳化硅含量和涂层微观结构对腐蚀行为的影响。长期电化学研究（210 天）表明， S7.5 的_por和 R_ct综合腐蚀研究和显微组织结果表明，搪瓷涂层钢筋的腐蚀行为与涂层微观结构密切相关，尤其是气孔和微裂纹。此外，还提出了电解质渗透退化和“自我修复”等增强的竞争机制，以解释不同涂层钢筋的腐蚀演化模式。这项工作的发现使人们对碳化硅/搪瓷复合涂层的腐蚀行为有了深入的了解，并为长寿命 RC 结构提供了解决方案。