Effect of Pre-immersion Temperature on Corrosion Product Films and Their Erosion Corrosion Resistance on 90/10 and 70/30 Copper-Nickel Tubes in 1 wt.% NaCl Solution

Both 90/10 and 70/30 copper-nickel tubes were immersed at different temperatures (10, 25 and 35 °C) for 30 days and then tested at 3 and 5 m/s to evaluate the erosion corrosion resistance of the corrosion product films formed during the immersion process. The results show that the corrosion product film formed at 35 °C has the best erosion corrosion resistance for both 90/10 and 70/30 copper-nickel tubes. The cupric corrosion products (Cu₂(OH)₃Cl) on the surface of 90/10 and 70/30 copper-nickel tubes are important to the erosion corrosion resistance which is related to the polymorphic structure of Cu₂(OH)₃Cl. The pre-immersion of 90/10 and 70/30 copper-nickel tubes at a high temperature (35 °C) is beneficial to the formation of corrosion product film with good erosion corrosion resistance, which contains thermodynamically stable Cu₂(OH)₃Cl (clinoatacamite), indicating the maturing of the corrosion product film. Pre-immersion at lower temperatures (10 °C) is unfavorable to the formation of film with good erosion corrosion resistance. Both 90/10 and 70/30 copper-nickel tubes should avoid low-temperature immersion during service. Additionally, raising the immersion temperature of seawater can improve the erosion corrosion resistance of 90/10 and 70/30 copper-nickel tubes.