Abstract
Electroplating in dilute Ni2+ electrolyte over limiting current density has been investigated as the blackening method for the electrogalvanized steel sheet.
The structure of the black deposits on the electrogalvanized steel sheet was analyzed by the X-ray diffraction method, scanning electron microscope, X-ray photoelectron spectrometer and glow discharge spectrometer and it was found that the surface of the black electrogalvanized steel sheet was partly covered with small Ni granules of about 0.1 μm in diameter.
The small Ni granules were covered with Ni, Zn, and composite compounds, such as Ni (OH)2, NiO, Ni2O3, Zn(OH)2 or ZnO and further covered with Zn(OH)2, ZnO of around 100 Å thick.
