Kinetic studies of iron metal particle degradation at various temperature and humidity conditions

Passivated iron metal particles suitable for use in magnetic recording media were exposed to various water concentrations at different temperatures to determine their magnetic and chemical stabilities. It was observed that degradation of the magnetic moment was affected more by increases in water concentration than by increases in temperature. Coercivity, however, was less affected under these conditions. The degradation of the magnetic moment of the iron particles was observed in two stages; a rapid initial stage followed by a much slower second stage was evident by measurements of the magnetic moment as a function of the exposure time to high temperature and humidity. The degradation products of these particles were identified by electron diffraction techniques as amorphous Fe304. The rate of degradation in both stages was modeled to be pseudo-zero order. Life expectancies of these particles from Arrhenius relationships are predicted