Corrosion Mitigation of Steel by Al-Zn Thermal Spray Coatings: Real-Time Monitoring with Optical Fiber Sensors

Abstract Thermal spray metallic coatings are commonly used to protect steel substrates from corrosion by acting as physical barriers. However, their porous microstructure can permit the ingress of water, oxygen, and corrosive agents, potentially leading to localized corrosion, such as pitting, beneath the coating. To enhance corrosion mitigation, selecting effective coatings and employing real-time monitoring techniques is crucial. This research investigates the corrosion mitigation performance of two different Zn-Al thermal spray coatings, Zn-Al pseudo alloy and Zn-15Al alloy, on steel substrates. The corrosion resistance and propagation of these coatings are compared by using distributed fiber optic sensors (DFOSs). DFOSs, utilizing optical frequency domain reflectometry (DFOR), offer high spatial resolution, distributed sensing capability, and superior environmental durability, making them ideal for detecting and monitoring corrosion. The findings demonstrate the superior performance of the Zn-Al coatings in corrosion mitigation and showcase the effectiveness of DFOS for continuous, real-time monitoring and quantitative assessment of corrosion behavior in thermal spray coated steel, particularly in challenging industrial and coastal environments.