Thermal analysis of magnesium reactions with nitrogen/oxygen gas mixtures.

•Total oxidation and nitridation heat decreases linearly from 79% to 95% N2 in O2/N2 mixture.•Preference of oxidation was weakened by nitridation in higher N2/O2 ratio mixture than air.•Two growth stages of coating layer are identified in entire Mg oxidation/nitridation process.•Activation energy can be derived from TG data for entire Mg oxidation instead of nitridation.