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 degrees 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 degrees 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 degrees 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 degrees 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.