An approach to fabricating protective coatings on a magnesium alloy utilising alumina

There are various methods available to enhance the corrosion resistance of magnesium alloys. Here, through utilising microstructure observations and phase identification, we show that, even with stable alumina, magnesium alloys can have their surface strengthened. Active magnesium atoms can be utilised to reduce the alumina and produce aluminum atoms. Aggregation of aluminum atoms on the magnesium alloy surface leads to an Al-rich intermetallic layer, which could enhance the corrosion resistance of the magnesium alloy. This is a new approach to protect magnesium alloys which takes advantage of the activity of magnesium atoms to fabricate protective coatings. •An Al-rich coating was fabricated using stable alumina on a magnesium alloy.•Mg ions penetrate the vacation-rich MgO lattice and reduce alumina into Al atoms.•Mg gas leaves the intermetallic melt and passes the porous MgO to reduce alumina.•Al atoms penetrate the vacation-rich MgO lattice to arrive the Mg alloy matrix.•Al atoms react with HCl to form AlCl3 and AlCl3 arrives the matrix through pores.