The effects of vanillin and anisaldehyde on electrodeposition of zinc-cobalt alloys onto AISI 1018 carbon steel were studied in an alkaline gluconate zincate electrolyte. The influence of an additive on the metal discharge depends on the structure of the added molecule and on the nature of the substrate. The composition of the deposit varies during the electrodeposition process. Maximum cobalt content is observed close to the steel-ZnCo interface for ZnCo formed with or without vanillin, but the composition profile becomes more uniform when anisaldehyde is added to the bath. The morphology of Zn-rich Co-alloy coatings was evaluated: Cobalt ions produce porous ZnCo alloys; vanillin induces slightly porous deposits, whereas uniform and more compact deposits were observed with anisaldehyde. Furthermore, a crystallographic study showed that the orientation of the lattice planes changes, with highly oriented deposits produced in the presence of anisaldehyde.