The pitting susceptibility of nickel in 0.08M Cl− solutions (pH 4.0 ) has been determined by both potentiodynamic and potentiostatic techniques, the former giving a pitting potential and the latter an induction time, , for pit initiation. The potentiostatic approach is preferred because of the good reproducibility of results. Samples were prepassivated in non‐Cl− or Cl− containing solutions and then potentiostatically polarized in 0.08M Cl− at different potentials and measured. For either pretreatment, decreased exponentially as the potential of pitting increased, i.e., . Oxides on samples prepassivated in Cl− solution contain incorporated Cl− and are significantly more resistant to pitting than those formed in Cl−‐free solutions. This increase in pitting resistance for the Cl−‐treated samples is in contrast to their decreased resistance to open‐circuit breakdown. Cl− incorporation results in ∼2% expansion of the lattice leading to a more defective and thus less stable film towards open‐circuit breakdown. The results strongly suggest that Cl− incorporated in the oxide lattice (as distinct from Cl− in the electrolyte) is not a precursor to pit initiation since it actually increases the resistance to pitting.