In　this　work,　three　types　of　fully　dense　aluminum-based　(Al)　coatings　(pure　Al,　AA2219　and　AA6061)　were　deposited　on　AZ31B　magnesium　(Mg)　alloy　by　a　recently　developed　in-situ　micro-forging　assisted　cold　spray　process.　The　detailed　microstructure,　coating　adhesion　and　corrosion　protection　performance　were　systematically　investigated.　Results　show　that　the　porosities　of　the　pure　Al,　AA2219　and　AA6061　coatings　are　as　low　as　0.34　±　0.11%,　0.23　±　0.09%　and　0.24　±　0.08%,　respectively.　Strong　adhesion　strength　(83.6–91.5　MPa)　was　achieved　for　the　Al-based　coatings　due　to　the　in-situ　micro-forging　induced　enhanced　mechanical-interlocking　between　Al-based　coating　and　the　magnesium　alloy　substrate.　The　corrosion　current　density　of　the　AZ31B　Mg　alloy　decreases　to　1.9–5.8　μA　cm−2　from　312.8　μA　cm−2　after　coated　with　the　Al-based　coatings.　The　long-term　corrosion　tests　further　indicate　that　the　Al-based　coatings　are　not　aqueous　solution　permeable　during　the　entire　1000　h　immersion,　thus　provided　robust　long-term　corrosion　protection　of　AZ31B　Mg　alloy　substrate.　Moreover,　the　difference　in　corrosion　resistances　among　the　three　Al-based　coatings　was　observed　and　was　further　explained　based　on　their　unique　microstructures　arising　from　the　coating　deposition　process.　The　present　in-situ　micro-forging　assisted　cold　spray　process　shows　great　potential　for　economical　and　effective　corrosion　protection　of　magnesium　alloy　and　provides　more　freedom　for　industries　to　design　and　use　magnesium　alloy　parts.　©　2019　Elsevier　B.V.