Two-dimensional pitted corrosion localization on coated steel based on fiber Bragg grating sensors

Steel is widely used as building material for large-scale structures, such as buildings, bridges, and oil and gas pipelines, due to its high strength-to-weight ratio. Corrosion has been believed to be one of the main reasons for reducing the load carrying capacity and the service life of structural steel, especially for the structures in harsh service environments. To mitigate corrosion for structural steel, coatings have been widely applied. On the other hand, to monitor corrosion in real time, embedding fiber Bragg grating (FBG) inside the coatings becomes a potential solution for coated steel structures. However, due to the fact that FBG sensors are local point sensors, the localization of pitted corrosion based on these sensors is very challenging. In this study, a methodology based on a three-sensor network was set up to detect the location and severity of the pitted corrosion on steel structures in two dimension (2D). The 2D simply supported plate theory together with the numerical simulation based on finite element analysis (ANSYS software) was used to derive the transfer function of the pitted corrosion location to the FBG sensor reading. Depending on the parametric study through numerical analysis, a pitted corrosion location exhaustion algorithm was successfully programmed. To verify the feasibility of this algorithm, laboratory experiments were carried out using a steel pipe with three FBG sensors and a temperature compensation sensor embedded inside a layer of epoxy coating (Duralco 4461). The experimental results indicated that the proposed methodology has potential to locate and assess the pitted corrosion on steel structures.