Electrochemically controlled pitting corrosion in Ni film: A study of AFM and neutron reflectometry

Electrochemical behavior of pitting corrosion of a Ni film, grown on Si substrate by sputtering, prepassivated in a chloride-free sulfuric acid solution and subsequently exposed to chloride above the pitting potential is reported. Specular and off-specular unpolarized neutron reflectometry and Atomic Force Microscopy (AFM) techniques have been used to determine the depth profile of scattering length density and morphology of as-deposited as well as corroded sample. Specular neutron reflectometry measurement of the film after corrosion shows density degradation along the thickness of film. The density profile as a function of depth, maps the growth of pitting and void networks due to corrosion. The AFM and off-specular neutron reflectivity measurements has suggested that the morphology of the film remains same after exposure of the film in chloride solution.