Electrochemical Aspects of the Cadmium Impregnation Process

• Published in: Journal of the Electrochemical Society 1980-12, Vol.127 (12), p.2535-2544
• Main Authors: Palanisamy, T., Kao, Y. K., Fritts, D., Maloy, J. T.
• Format: Article
• Language: English
• ISSN: 0013-4651; 1945-7111
• DOI: 10.1149/1.2129515

Electroanalytical methods have been employed to investigate the cathodic deposition of Cd(OH)2 on a Ni substrate from Cd(NO3)2 solution. At potentials positive of -- 0.6V vs. SCE a gray noncrystalline form of Cd)OH)2 appears to be deposited on the Ni substrate, presumably via a precipitation mechanism using the OH -- that is electrogenerated in the reduction of NO3 -- . At potentials negative of -- 0.8V vs. SCE, a black precursor to Cd(OH)2 is deposited. This black material forms at the same potentials as one of the further reduction processes of NO3 -- and NO2 -- that is reported herein; hence, it is believed to involve a Cd complex of a nitrate reduction product. X-ray diffraction studies indicate that either of these materials is readily converted to crystalline hexagonal Cd(OH)2 during the electrochemical formation process. However, since the gray material is deposited with min. concurrent gas evolution or metallic Cd deposition, its utility in achieving high Cd(OH)2 loading of a uniform material within the pores of Ni plaque material is stressed. When low current densities (0.2 A/in.2 plaque) are employed (such that the potential of the Ni substrate never becomes more negative than -- 0.65V vs. SCE) in the deposition; a high loading is achieved of a uniformly distributed product that requires no formation to reach max. capacity.7 refs.--AA