Galvannealed coatings are obtained by heat treating galvanized steel strips and are widely used in the automotive industry due to their improved properties. The variables influencing coating formation on high strength low alloy steel (HSLA) were analyzed. The study was carried out on samples obtained from an industrial plant and on samples coated in a hot dip process simulator. The mechanical properties of the steel substrate were evaluated, and the morphology and Fe content in the various phases of the coating and its characteristics were analyzed and compared. It was found that the Fe-Zn phases can be controlled and performed varying the temperature and holding time during the annealing cycles, avoiding the formation of undesirable phases.