The invention provides a chemical-mechanical polishing composition comprising alpha alumina, fumed alumina, silica, an oxidizing agent that oxidizes nickel-phosphorous, oxalic acid, optionally, tartaric acid, optionally, a nonionic surfactant, optionally, a biocide, and water. The invention also provides a method of chemically-mechanically polishing a substrate comprising contacting a substrate with a polishing pad and the chemical-mechanical polishing composition, moving the polishing pad and the polishing composition relative to the substrate, and abrading at least a portion of the substrate to polish the substrate.