Abstract: A method of coating of thin film coated magnetic disks and thin film magnetic disks made thereby is described. In accordance with the invention, a barrier layer is deposited on the substrate before the underlayer film(s) to increase the corrosion resistance of metallic substrate magnetic disks and, in the case of nonmetallic substrates, to reduce the diffusion of water to the substrate and of freely moveable ions from the substrate. Preferably the barrier layer is deposited by medium frequency pulsed sputtering at a frequency of 10 to 200 kHz and a pulse length to pulse pause ratio from 5:1 to 1:10. Aluminum or chromium are the preferred materials for the barrier layer. Additional improvements may be achieved where the sputtering process gas contains a proportion of oxygen and/or nitrogen.