日本金属学会誌

J. Japan Inst. Metals, Vol. 59, No. 8 (1995),
pp. 840-845

Corrosion Behavior of TbFeCo Magneto-Optical RecordingFilms with Protection Coating in Aqueous Environment

Noboru Akao, Eiji Shimizu and Katsuhisa Sugimoto

Department of Metallurgy, Faculty of Engineering, Tohoku University, Sendai

Abstract:

Corrosion behavior of sputter-deposited TbFeCo magneto-optical recording films with protection coating has been studied in an aqueous solution. Specimens having Si3N4 (0{~}234 nm)/Tb0.33Fe0.48Co0.19 (74 nm)/glass structure were prepared and an immersion corrosion test and an electrochemical impedance measurement of the specimens were performed in 1.0 kmol⋅m-3 Na2SO4 of pH6.30.
The corrosion morphology of the specimens in the solution was pitting, which started from pinhole defects in Si3N4 protection films. The morphology changed with the thickness of the protection films. The selective dissolution behavior of alloying elements in TbFeCo films into the test solution also changed with the thickness of the protection films.

Electrochemical impedance diagrams changed with the progress of pitting corrosion on the specimens. After an analysis using an electrical equivalent circuit of the corroding system, the values for the charge transfer resistance and the relaxation coefficient were found to decrease with the growth of pitting corrosion.


(Received February 7, 1995)

Keywords:

TbFeCo thin films, magneto-optical recording media, protection coating, corrosion resistance, pitting, electrochemical impedance, electrical equivalent circuit


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