Abstract
The electrochemical measurement was carried out in order to determine the localized attack in the nickel-chromium (Ni-Cr) electroplates and also the microscopic study was applied for the examination of the corroded surface of the Ni-Cr coating in an attempt to elucidate the mechanism of the corrosion in the Ni-Cr electroplates.
The corrosion of the Ni-Cr electroplates at the potential region of the active state of nickel such as at -0.34- +0.1V vs. S. C. E. might correspond to the anodic dissolution of nickel through the pores or cracks in the chromium coating in Ni-Cr electroplates.
The corrosion pits of the Ni-Cr electroplates observed in acid sulfate solution are hemispherical in shape and the radii of the pits were found to increase with the rate of dissolution of the Ni-Cr electroplates.
It was found that the corrosion pits of the nickel layer were always in the sites of the cracks of the chromium and the pattern of the corrosion pits was a kind of reproduction of the cracks in chromium coating.
The dissolution of nickel along the crevice of the chromium coatings was found to be pronounced when the concentration of chloride ions was increased in the sulfate solution.
Incorporated sulfur in the bright nickel had a similar effect on the corrosion of Ni-Cr electroplates giving larger corrosion current in the sulfate solution.
