Monitoring the passivation and depassivation of reinforcement steel is of significant importance, particularly for certain reinforced concrete structures that define the time of steel rebar depassivation as the end of the durability service life. In this study, a gold-sputtered long-period grating (LPG) optical fiber sensor coated with pulse-electroplated iron-carbon is characterized for continuous monitoring of the surface state of carbon steel from passivation to depassivation in concrete pore solutions. Electrochemical corrosion and optical tests are performed simultaneously using an electrochemical workstation and an optical instrument. A protective passivation film with a thickness of approximately 4.05 nm was formed on the iron-carbon coating after 5 days of immersion in the simulated concrete pore solution, and its thickness is nonlinearly correlated with the wavelength shift of the LPG optical fiber sensor during the passivation process. The resonant wavelength changes in the opposite direction after depassivation, which can be used for the detection of the depassivation time. After depassivation, the wavelength shift and mass loss of the iron-carbon coating can be divided into three phases, and a linear relationship exists in each phase. The gold-sputtered fiber sensor coated with pulse-electroplated iron-carbon investigated in this study, demonstrates better performance than silver-deposited LPG fiber sensors.

监测钢筋的钝化和去钝化非常重要，特别是对于某些将钢筋去钝化时间定义为耐久性使用寿命终点的钢筋混凝土结构。在这项研究中，涂有脉冲电镀铁碳的金溅射长周期光栅（LPG）光纤传感器的特点是连续监测混凝土孔隙溶液中碳钢从钝化到去钝化的表面状态。使用电化学工作站和光学仪器同时进行电化学腐蚀和光学测试。在模拟混凝土孔隙溶液中浸泡5天后，铁碳涂层上形成了厚度约为4.05 nm的保护性钝化膜，其厚度与钝化过程中LPG光纤传感器的波长偏移呈非线性相关过程。去钝化后谐振波长向相反方向变化，可用于去钝化时间的检测。去钝化后，铁碳涂层的波长漂移和质量损失可分为三个阶段，并且每个阶段之间都存在线性关系。本研究中研究的涂有脉冲电镀铁碳的金溅射光纤传感器表现出比银沉积液化石油气光纤传感器更好的性能。