Hydrogen absorption and embrittlement of austenitized Zn–Al–Mg-coated medium-Mn steel

In this study, we investigated hydrogen absorption during austenitizing, as well as the resistance to hydrogen embrittlement (HE), in Zn-Al-Mg-coated medium-Mn steel in comparison to Zn-Al-coated steel. After austenitization at 750 °C for 5 min, the Zn-Al-Mg-coated steel had a higher hydrogen content than the Zn-Al-coated steel, likely due to the reaction of Mg with water vapor in the furnace atmosphere, which led to the formation of an MgO layer on the outermost surface. Despite the higher hydrogen content, silver decoration analysis revealed that most of the absorbed hydrogen remained confined within the coating layer, limiting its diffusion into the steel substrate and thereby maintaining HE resistance comparable to that of the Zn-Al coated steel.