A cobalt-chromium (Co-Cr) magnetic film electrodeposited on the surface of an aluminum alloy. A process for making an aluminum alloy electrodeposited a cobalt-chromium (Co-Cr) magnetic film comprises the steps of chemically polishing an aluminum alloy substrate, pretreating either with phosphate or with zincate and electrodepositing in a plating bath containing cobalt and chromium ions to prepare the cobalt-chromium thin film on the aluminum alloy. Chromium content in the film can be designed by adjusting the parameters of pretreatment and electroplating. The produced cobalt-chromium film can flexibly adjust the magnetic characteristics (e.g. coercive force (Hc) and ramanence magnetization (Mr)) and is suitable for use in a magnetic recorder. The chemical composition, adhesion, microhardness, magnetic properties of the deposits indicate that the Co-Cr films produced are satisfactory for magnetic recording service.