Regeneration-repair-strengthening mechanism in the oxidation film damage region of copper-nickel alloys under magnetic field effects

Copper-nickel alloy pipes in marine environments are prone to scouring by solid particles, which disrupt the bilayer film and induce scratches. These scratched regions are more vulnerable to perforation, potentially leading to premature pipe failure. Thus, rapidly repairing the film and restoring its corrosion resistance is a major challenge. This study simulates the “film damage-regeneration” process of copper-nickel alloys in marine environments, researching the regeneration of the film in scratched regions of a 70/30 Cu-Ni alloy in a 3.5 wt% NaCl solution, under both nonmagnetic and magnetic field conditions. The results demonstrate that the application of a magnetic field accelerates the initial regeneration of the film and the recovery of its corrosion resistance, and through synergistic interactions with the scratched microregions, it alters the local pH conditions, suppresses the re-deposition of Cu2O, and significantly enhances the enrichment of NiO on the surface of the regenerated film. Ultimately, a single-layer film structure with enhanced corrosion resistance is formed. This study shows that magnetic fields speed film regeneration on scratched 70/30, Cu-Ni alloys in seawater, yielding the NiO-rich single-layer film with improved, corrosion resistance and offering a new way to extend marine engineering equipment lifespan.