pH-Dependent Pitting Corrosion in Nickel Thin Films

Nickel thin films are widely used in applications requiring corrosion resistance, but in chloride environments, localized breakdown of the passive layer can lead to pitting corrosion. This study investigates the pitting behavior of Ni thin films in chloride solutions with glycine and calcium ions as inhibitors, under varying pH. Oxygen plasma treatment induced surface defects that modulated pit density. At low pH, severe corrosion was observed, while higher pH led to passivation via nickel oxide and calcium carbonate formation. Microscopy and XPS analyses revealed pH-dependent changes in pit morphology and density. Under intermediate pH, localized redeposition of nickel was detected at pit centers, forming nanoscale features. Finite element simulations confirmed that pit geometry creates a chemical potential gradient driving inward metal flux. These results advance the understanding of pitting corrosion in nickel films and highlight the influence of pH, inhibitors, and surface condition on corrosion processes.