An AFM Study of corrosion on rigid magnetic disks

The corrosion susceptibility of a cobalt-based magnetic alloy as a function of overcoat film thickness at 20 °C and 50% relative humidity is investigated using atomic force microscopy. The overcoat films include ion beam-deposited nitrogenated carbon (IBDN), and sputter-deposited silicon carbide (SiC) and silicon nitride (SiNx). In all cases, corrosion decreases with increasing overcoat film thickness. The critical overcoat film thickness for corrosion inhibition is approximately 25, 25 and 20 Å for IBDN, SiC and SiNx, respectively. However, larger corrosion particles are found for IBDN and SiC with increasing thickness just below the critical thickness for coverage.