Evaluation of Damage Tolerance for TSA-Coated Steel in a Simulated Marine Environment

Abstract Thermal Spray Aluminium (TSA) coatings are widely used to protect steel structures in marine environments due to their ability to provide long-term cathodic protection and their low self-corrosion rates. Even when mechanically damaged, TSA remains effective, as aluminium is galvanically more active than steel. However, the extent of damage that can be tolerated without compromising performance is not fully understood. This study investigates the electrochemical performance of TSA-coated steel with 30% (TSA_30) and 50% (TSA_50) exposed steel surfaces. The TSA coating (300 μm thick, 1050 AA) was applied using the twin-wire arc spray method. Samples were immersed for 30 days in synthetic seawater (ASTM D1141-98, without heavy metals) under stagnant conditions at 18 °C. Results showed that both TSA_30 and TSA_50 provided adequate cathodic protection throughout the exposure period. After removing calcareous deposits formed on the exposed steel, rapid formation of aragonite was observed, which contributed to a reduction in the corrosion rate of the coating. These findings highlight the coating's high damage tolerance and its ability to maintain protective performance even in the presence of a significant defect. This study suggests that TSA coatings offer a robust safety margin, which could help reduce inspection frequency and maintenance costs in marine applications.