A recording medium having an outer surface relatively free of magnetic particulates is achievable by, after forming a magnetic recording layer with which magnetic contamination is associated, removing magnetic contamination from the medium by immersing the medium in an acidic water solution. For example, a post-sputter wash process utilizing a mildly acidic water solution having a pH less than around 5 may remove cobalt particle contaminants from the surface of the medium. The water solution may be acidized by introducing into deionized water a pre-diluted strong acid such as nitric acid or a weak acid such as carbonic acid.