The　use　of　alkali-activated　cementitious　materials　(AACMs)　and　sea　sand　to　prepare　mortar　can　help　reduce　the　high　carbon　dioxide　emissions　associated　with　ordinary　Portland　cement　and　alleviate　the　shortage　of　natural　aggregates.　However,　the　chloride　ions　present　in　sea　sand　can　increase　the　risk　of　rebar　corrosion.　Compared　with　traditional　cements,　AACMs　may　offer　superior　chloride　ion　binding　capacity.　Alkali-activated　slag/sea　sand　(AASS)　mortars　with　varying　alkali　dosages　were　prepared　in　this　study.　First,　the　mechanical　properties　of　the　AASS　mortars　were　tested.　Subsequently,　electrochemical　methods,　including　chloride　ion　fixation　and　pH　analysis,　were　used　to　evaluate　the　corrosion　resistance　of　rebars.　The　results　showed　that　an　increase　in　alkali　dosage　enhanced　both　the　pH　and　the　chloride　ion　fixation　capacity,　improving　the　corrosion　potential,　reducing　the　corrosion　current　density　and　increasing　the　polarisation　resistance.　Electrochemical　impedance　spectroscopy　tests　indicated　optimal　corrosion　resistance　at　a　6%　alkali　dosage,　with　the　best　rebar　passivation　at　this　level.　Analysis　of　hydration　products　revealed　how　the　increased　alkali　dosage　boosted　chloride　ion　fixation　and　rebar　corrosion　resistance.　The　results　of　this　work　provide　a　theoretical　basis　for　the　application　of　AASS　mortar　in　construction.