The disk lubricant tank of the present invention includes a lubricant bath cover device that resides on the lubricant bath surface to suppress surface waves. The bath cover includes a plurality of finger-like projecting members that define a plurality of disk passage slots therebetween. A plurality of disks are disposed upon a disk holding mandrel and are lowered into the lubricant bath. Each disk passes through a separate disk passage slot during the dipping process. The finger-like projections reside on the bath surface between the disk to suppress surface waves that would otherwise impinge upon side surfaces of the disk, leading to lubricant overcoat areas upon the side surfaces of the disk. Therefore, hard disks of the present invention are formed with a more uniform lubricant coating wherein unwanted lubricant overcoat areas formed by surface waves in the lubricant bath are suppressed.