An investigation of the effect of a magnetic field on the phosphate conversion coating formed on magnesium alloy

•A magnetic field has been adopted in phosphate process for magnesium alloy.•An external magnetic field enhances the formation and desorption of many small hydrogen bubbles at magnesium alloy/solution interfaces.•An external magnetic field causes a uniform distribution of the Mg2+ concentration during the formation of phosphate conversion coating.•The superimposed magnetic field can improve the quality of phosphate conversion coating.