The invention relates to composite sacrificial anodes, particularly but not exclusively, based on magnesium, and to methods for their production. The composite sacrificial anode (10) for immersion in a corrosive environment comprises a plurality of castings (12) of a sacrificial material each disposed around a corresponding electrical connector for attachment to a structure to be protected, at least a part of the surface of each segment (12) being protected from corrosion by the environment by being adjacent at least one other segment (12), wherein the castings are connected together electrically only via their electrical connectors. A method of producing a composite sacrificial anode for immersion in a corrosive environment is also described, the anode (10) having an electrical connection for attachment to the structure to be protected, which method comprises casting a plurality of segments (12) of a sacrificial material each in contact with a corresponding electrical connector, each connector being at least partly within its corresponding individual segment (12), and electrically connecting the segments together only via their electrical connectors.