Nickel–aluminum bronze is a key structural material for marine propellers, yet its corrosion behavior under dynamic seawater erosion remains inadequately elucidated. To clarify the corrosion kinetics under high-speed dynamic seawater erosion of the ZCuAl10-4-4-2 marine copper alloy, erosion–corrosion tests and multi-method characterizations were conducted. The results illustrate that the α phase exhibited a higher corrosion susceptibility, driving micro-damage evolution: κ/α interface crack initiation at 4 h, significant crack propagation with a dense κ_II phase at 24 h, and pit formation (≈100 μm) at 48 h. Dynamic erosion induced critical electrochemical changes at 4 h and 24 h, with reduced charge transfer resistance, lower corrosion potential (E_corr) and elevated current density; the 24 h stage showed the peak corrosion rate due to unstable, spallable corrosion product films. Prolonged erosion–corrosion promoted the formation of a stable protective corrosion product layer, which enhanced the alloy’s corrosion resistance and reduced its corrosion rate.