The influence of Dy content on the corrosion resistance of sputter-deposited TbDyFeCo alloy films for magneto-optical recording media was investigated by means of immersion corrosion tests and electrochemical polarization measurements. Surface films on the alloy were analyzed by X-ray photoelectron spectroscopy (XPS) after the immersion corrosion tests. As reference specimens, TbDyFeCo alloy tapes prepared by a melt span method were also used. The corrosion mass loss of the alloy films in 0.01 kmol·m-3 NaCl increased with increasing Dy content of the films. The same results were obtained on the alloy tapes. The selective dissolution of Fe and Co to test solutions and the concentration of Tb and Dy in surface films were found after the immersion corrosion tests. Surface films on TbDyFeCo alloys were composed of hydroxides and oxides of Tb, Dy and Fe. The quantities of hydroxide and oxide of Dy increased after the immersion corrosion tests. Anodic current densities in both the active and passive states increased and the pitting potential decreased with increasing Dy content of the alloys. This shows that stability of passive films is deteriorated by the Dy addition to the alloy.
|Number of pages
|Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals
|Published - 1994