Methods for forming polymeric protective layers on magnesium anodes for magnesium batteries include placing a solution of electropolymerizable monomers onto all exposed surfaces of a magnesium anode, and electropolymerizing the monomers in the solution. The monomers can be glycidyl methacrylate, a salt of 3-sulfopropyl methacrylate, or a mixture of the two. Protected magnesium foam anodes for 3-D magnesium batteries have a magnesium foam electrolyte, and a polymeric coating covering all exposed surfaces of the magnesium foam electrolyte. The polymeric protective coating formed of (poly)glycidyl methacrylate, poly(3-sulfopropyl methacrylate), or a copolymer of the two.