磁気ディスクにおける腐食性評価

概要

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The corrosion mechanisms of magnetic recording media in a high humidity environment were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and a metal elution test, where drops of nitric acid on the media surface were analyzed by inductively-coupled plasma mass spectrometry (ICP-MS) measurement (droplet-method). By observing SEM images, the corrosion on the media surface was found to have accelerated with longer exposure to the high humidity environment. Moreover, the cross-sectional TEM images proved that the lower NiP layer was invaded by moisture from the dented part of the magnetic layer due to its texture. In addition, the droplet-method analysis revealed that Co and Cr in the magnetic layer and Ni in the plated NiP layer were found to have eluted through the diamond-like carbon (DLC) film by drops due to nitric acid. The relation between the elution behavior of the elements and the corrosion process was clarified by adjusting the time the media surface was in contact with the nitric acid droplets. Based on these results, a model mechanism for corrosion behavior due to the moisture is proposed.