Investigation of Corrosion Mechanisms and Protective Performance of Thermal Sprayed Aluminum Coatings on Steel Structures

This paper aims to investigate the corrosion and protection mechanisms of thermal sprayed aluminium (TSA) coatings. The open circuit potential (OCP), the linear polarisation resistance and the impedance spectrum were conducted by electrochemical measurement tests to analyse TSA coating corrosion behaviour. The microstructure analysis results revealed that the TSA coating formed a dense oxide layer, preventing contact between corrosive substances and the substrate. The polarisation resistance initially decreases and then increases, suggesting that the TSA coating possesses self-filling capability. The corrosion process of TSA coating consists of three stages: passivation film formation, pore blockage by corrosion product, and accumulation of corrosion products. The TSA coating provides cathodic protection in the damaged area, reducing the corrosion rate. Corrosion products accumulate over time, reinforcing material resistance to infiltration. A three-stage failure model describes the coating's degradation, comprising intact coating, localised damage, and final failure with the highest corrosion rate.