Monitoring Passivation, Pitting Corrosion Initiation, and Propagation of Steel Bar with Iron–Carbon Electroplated Long Period Fiber-Grating Sensor

Abstract

An iron–carbon electroplated long period grating (LPG) fiber sensor to monitor the passivation, initiation, and propagation of the pitting corrosion of steel bars is characterized in simulated concrete pore solutions. An inner silver is first deposited on the surface of LPG fiber before electroplating the outer iron-carbon layer. The surface topographies of both silver and iron-carbon layers are examined with atomic force microscopy. The corrosion evolution of an iron-carbon layer in different solutions is measured by using electrochemical impedance spectroscopy and linear polarization resistance, and the shift in the resonant wavelength of an iron-carbon electroplated LPG sensor is monitored with a spectrum analyzer. Experimental results show that iron–carbon electroplated LPG sensors can continuously monitor the passivation and initiation of pitting corrosion, while it is not suitable to monitor the propagation of pitting corrosion.