Selective oxidation of dual phase steel after annealing at different dew points

► Selective oxidation of a dual phase steel after annealing at different dew points. ► External selective oxidation of phosphorus occurred on steel surface annealed at 0°C dp. ► External selective oxidation of Mn, Si, and Al occurred on steel annealed at −60°C dp. ► Mo content increased as the depth from the surface of steels increased. Hot galvanized steels have been extensively used in the automotive industry. Selective oxidation on the steel surface affects the wettability of zinc on steel and the grain orientation of inhibition layer (Fe–Al–Zn alloy) and reduces the iron diffusion to the zinc layer. The aim of this work is to identify and quantify selective oxidation on the surface of a dual phase steel, and an experimental steel with a lower content of manganese, annealed at different dew points. The techniques employed were atomic force microscopy, X-ray photoelectron spectroscopy, and glow discharge optical emission spectroscopy. External selective oxidation was observed for phosphorus on steel surface annealed at 0°C dp, and for manganese, silicon, and aluminum at a lower dew point. The concentration of manganese was higher on the dual phase steel surface than on the surface of the experimental steel. The concentration of molybdenum on the surface of both steels increased as the depth increased.