Effect of Sealing Treatment with Fluorocarbon Sealant on Electrochemical Corrosion Behavior and Salt Spray Corrosion Resistance of 8YSZ Thermal Barrier Coating

The atmosphere plasma sprayed 8wt% Y₂O₃ stabilized ZrO₂ (8YSZ) thermal barrier coating was sealed with the sealant of fluorocarbon finish paint. The effects of sealing treatment on the microstructure, electrochemical corrosion behavior and salt spray corrosion resistance of the coating were investigated. The results show that the fluorocarbon finish paint permeated into the coating due to capillarity action. The surface roughness of the coating was reduced from 5.4 μm before sealing to 0.8 μm after sealing, and the contact angle increased from 61.99° before sealing to 70.58° after sealing. The self-corrosion potential of the coating decreased from -0.308 V before sealing to -0.42 V after sealing, indicating the sealing agent was anodic relative to the coating. After sealing, the passivation phenomenon of the coating was observed, the polarization resistance increased, and the self-corrosion current density decreased to 1.26×10^-6 A·cm^-2, indicating that the corrosion resistance of the coating increased. The fluorocarbon finish paint could provide a good sealing effect on the thermal barrier coating in the neutral salt spray environment, which could effectively inhibit the diffusion of Cl^- into the coating.