Effect of Oxide Film on the Cavitation Erosion-Corrosion Behavior of Nickel-Aluminum Bronze Alloy

The effect of oxide film on the cavitation erosion-corrosion of nickel-aluminum bronze (NAB) alloy in 3.5 wt% NaCl solution was investigated via pulse and continuous cavitation modes of ultrasonic vibrator device according to ASTM. NaCl solution was used to simulate the seawater condition of NAB alloy. In the same effective cavitation erosion time of 8 h, the total mass loss caused by continuous cavitation erosion-corrosion was 21.45±0.75 mg, which was almost 1.5 times as much as that of pulse mode. The synergistic effect of cavitation erosion and corrosion was analyzed. The results showed that the total contribution of the synergy component in the process of continuous cavitation erosion-corrosion was 51.66%, while it fell to 25.56% in the pulse mode. The open-circuit potential measurements and electrochemical atomic force microscope test demonstrated that the rapid repair of an oxide film during pulse cavitation played an important role in resisting the cavitation erosion-corrosion. Furthermore, the formation process of oxide film was in situ observed, indicating higher nucleation rate compared with its growth rate. Also, the alloy with such film exhibited lower synergy in pulse mode than that without film in continuous mode.