REPRODUCIBLE DIRECT EXPOSURE TESTING OF METAL EVAPORATED MAGNETIC MEDIA

Coupons (5 x 5 mm) of metal evaporated (ME) tape were exposed directly to variations of the Battelle Class II mixed flowing gas accelerated corrosion test environment at three different gas velocities in an imp inging jet geometry. The magnetic saturation moment of the coupons was measured before and after exposure. The samples lost magnetic saturat ion moment linearly with time. The moment loss was between 5 and 25% p er day. Gas phase mass transfer by convection and diffusion affected s ubstantially the loss of moment. Increasing the relative humidity in t he range of 40-70% strongly increased the corrosion rate. The flow geo metry and rate must be specified to perform meaningful accelerated exp osure studies of currently available ME tape.