N. Akao et al., INFLUENCE OF DY CONTENT ON AQUEOUS CORROS ION OF TBDYFECO MAGNETOOPTICAL RECORDING FILMS, Nippon Kinzoku Gakkaishi, 58(3), 1994, pp. 309-317
The influence of Dy content on the corrosion resistance of sputter-dep
osited TdDyFeCo alloy films for magneto-optical recording media was in
vestigated by means of immersion corrosion tests and electrochemical p
olarization measurements. Surface films on the alloy were analyzed by
X-ray photoelectron spectroscopy (XPS) after the immersion corrosion t
ests. As reference specimens, TdDyFeCo 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 fil
ms. The same results were obtained on the alloy tapes. The selective d
issolution 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 oxi
des of Tb, Dy and Fe. The quantities of hydroxide and oxide of Dy incr
eased after the immersion corrosion tests. Anodic current densities in
both the active and passive states increased and the pitting potentia
l decreased with increasing Dy content of the alloys. This shows the s
tability of passive films is deteriorated by the Dy addition to the al
loy.