During　the　growth　process　of　a　plasma　electrolytic　oxide　(PEO)　coating　on　an　AZ-31　Mg　alloy,　electric　breakdown　inevitably　occurs　and　causes　local　disintegration　of　the　coating,　thus　forming　breakdown　pores　that　result　in　an　increased　coating　porosity　and　suppressed　corrosion　resistance.　Here,　we　report　for　the　first　time　that　the　self-repairing　capability　of　the　PEO　process　can　restore　the　coating　after　breakdown　damage　by　decreasing　the　porosity,　tuning　the　components　and　improving　the　corrosion　resistance　via　the　deposition　of　electrolyte　anions　into　the　breakdown　pores.　Based　on　detailed　scanning　electron　microscopy　and　transmission　electron　microscopy　characterizations　of　the　PEO　coatings　processed　in　alkaline　silicate　electrolytes,　it　was　found　that　the　pores　were　repaired　by　silica　fillings　formed　by　the　plasma-induced　deposition　of　anions　(SiO32-)　in　the　electrolyte.　The　plasma-deposited　silica　possesses　short　Si-O　bond　lengths　that　are　manifested　by　an　Si-L-2　,L-3　edge　shift　by　similar　to　1.3　eV　to　higher　energies.　In　addition,　the　presence　of　some　amount　of　Mg　together　with　a　minor　admixture　of　K　indicates　the　contribution　of　ionic　migration　and　plasma　collisions　to　the　self-repairing　process　in　the　PEO　coating.　(C)　2018　Elsevier　B.V.　All　rights　reserved.