Cooperation strategy between the corrosion resistance of CoCrNi coatings and flame ablation temperature

CoCrNi coatings were prepared on Q235 substrates using High-Velocity Air Fuel (HVAF) and tested by ablation at 1100 °C, 1200 °C, 1300 °C, and 1400 °C for 600 s. No visible defects were observed on the coating's surface after ablation below 1300°C, while the coating melted after ablation at 1400 °C. Corrosion tests in a 3.5 wt.% NaCl solution were conducted to evaluate the coatings' corrosion resistance before and after ablation, and results showed that the ablated coatings had better corrosion resistance. The coating exhibited optimal corrosion resistance following ablation at 1300 °C, as evidenced by an improved self-corrosion current density (Icorr) of 0.3411 μA·cm-2 and a polarization resistance (RP) of 2502 kΩ. The primary reason for this phenomenon is that the dense chromium oxide transition layer that forms on the surface of the coating following ablation effectively blocks the intrusion of external corrosive media, thereby providing adequate protection for the substrate material.