The repassivation of nickel-copper alloys in sulphuric acid

The behaviour of freshly generated electrode surfaces of Ni, Ni-30Cu, Ni-50Cu and Ni-70Cu in 1.0 M H₂SO₄ has been investigated. At low potentials all metals grow a monolayer of film designated as MOH when M is Cu⁺ or Ni⁺. The kinetics of formation of this monolayer follows Tafel's equation. At higher potentials passivation of the metals occurs by film growth under high electric field, with two different sets of high field parameters for different film thicknesses. The rate of film growth for all metals is controlled largely by the nickel oxide component of the film.