Diamond-like film as a corrosion protective layer on the hard disk

A magnetic layer based on Go-alloys does not possess the necessary mechanic al durability and corrosion resistance and must be covered with a protectiv e layer. An accelerated electrochemical test has been conducted on a hard d isk magnetic layer covered with amorphous hydrogenated carbon doped with ni trogen. From the potentiodynamic and DC polarization measurements of the co rrosion current in a 0.15 M NaCl solution adjusted to different pH, it was concluded that an acid environment can largely decrease the reliability and lifetime of a hard disk. Lubricant can contribute to corrosion protection by covering voids and other overcoat imperfections and prevent water vapor penetration into the magnetic film. Atomic force microscope images show loc alized distribution of corrosion sites with a density of 1.2 x 10(6) defect s/cm(2). The overcoat also prevents a lateral spread of the corrosion produ cts across a disk. (C) 2000 Elsevier Science S.A. All rights reserved.