The erosion–corrosion behavior of 90/10 and 70/30 copper–nickel tubes was investigated by in situ electrochemical tests on a self-built loop apparatus and ex situ surface characterization. The corrosion product film that formed at 1.5 m/s for the 90/10 tube and at 0.5 m/s for the 70/30 tube showed the best corrosion resistance. For the 90/10 tube, a continuous film existed below 3 m/s and mainly inhibited a cathodic reaction. For the 70/30 tube, a continuous film existed in the range of 0.5–4.7 m/s and was more similar to typical passive film electrochemically, although it was cracked at 4–4.7 m/s. So, the “critical flow velocity” of the 90/10 tube was between 3 m/s and 4 m/s, and that of the 70/30 tube was beyond 4.7 m/s.

Nickel–aluminum bronze (NAB) is widely used to fabricate flow-handling components because of its good cavitation corrosion (CE) resistance and superior casting property. The existence of different phases, e.g., the α phase, β phase and κ phase, can cause significant selective phase corrosion on NAB. However, under the action of CE with different times, the influence of these phases on the corrosion behavior of NAB, including selective phase corrosion and uniform corrosion, needs to be further studied, which can contribute to a deep understanding of the CE mechanism of NAB in corrosive media. In this work, the corrosion behavior of NAB in 3.5 wt.% NaCl solution after different CE times was evaluated by electrochemical noise (EN), combined with scanning Kelvin probe force microscopy (SKPFM) and morphology analysis. The results showed that the corrosion behavior of NAB was closely associated with the variation in its complex microstructure after different CE times. Selective phase corrosion played a crucial role in the surface damage before 0.5 h of CE. With the prolongation of CE time, the stripping of κ phases decreased the degree of selective phase corrosion of NAB. As a result, both selective phase corrosion and uniform corrosion presented equal performances after 1 h of CE. However, after CE for 2–5 h, uniform corrosion had a dominant impact on the surface damage of NAB. Eventually, the corrosion mechanism of NAB after different CE times was clarified based on the relevant experimental results.

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