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 °C. Corrosion protection performance of three different coatings (initial spray powder were 100% Al, 70% Al + 30% A12O3 and 50% Al+50% A12O3 respectively) on 20^# carbon steel pipe was analyzed by weight loss, macro-appearance, microstructure and chemical component analysis. The results showed that cold sprayed A1/A1₂O₃ coating could protect the pipe substance from corrosion under insulation effectively. When A1₂O₃ 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% Al₂O₃ was most suitable for using in engineering.