Corrosion Behavior of 20^# Carbon Steel with Cold Sprayed Al-Al₂O₃ Coatings under Insulation

Immersion tests were conducted to simulate the corrosion under insulation (CUI) in 0.01%, 0.1% and 1% NaCl solution at 80℃. Corrosion protection performance of three different coatings (initial spray powder were 100% Al, 70% Al+30% Al₂O₃ and 50% Al+50% Al₂O₃ respectively) on 20^# carbon steel pipe was analyzed by weight loss, macro-appearance, microstructure and chemical component analysis.The results showed that cold sprayed Al/Al₂O₃ coating could protect the pipe substance from corrosion under insulation effectively. When Al₂O₃ was added into spray powder, the deposition efficiency and hardness increased, but the corrosion resistance decreased. Overall, considering both corrosion resistance and strength, the coating sprayed with 70% Al+30% Al₂O₃was most suitable for using in engineering.