CORROSION OF METAL PARTICLE AND METAL EVAPORATED TAPES

Abstract

Very high coercivity metal particle (MP) and metal evaporated (ME) tapes were initially intended for 8mm video and digital audio tape applications, but more recently they are used for digital data recording applications. In view of the inherent susceptibility of such media to environmental corrosion, a number of recent studies have addressed their long term stability and archivability using accelerated tests of elevated temperature-humidity (T-H) or polluting gas atmospheres (Battelle). In this study we investigated the corrosion stability of commercial 8mm Hi8MP and ME tapes and of experimental Ba-ferrite (BaFe) tapes, based on the change in digital error rates after exposure to a T-H test at 50°C and 80%RH for 7.5 weeks. We observed a large increase in errors for all the MP and ME tapes studied, but also a large variation in corrosion stability among the tapes from different manufacturers. This large increase in errors may be due to a change in the magnetization of the tapes--particularly in the critical 0.3 micron region near the surface of the tapes which contributes most of the signal at the 53 kfci recording density used for the test--or to a change in the surface morphology of the tapes, or a combination thereof. The BaFe tapes were essentially immune to corrosion.