The　shortages　of　river　sand　and　freshwater　in　marine　engineering　can　be　addressed　by　utilizing　seawater　and　sea　sand　concrete　(SWSSC).　However,　the　sulfate　resistance　of　SWSSC　at　low　temperature　is　not　clear.　In　this　study,　the　seawater　and　sea　sand　cement　mortar　(SSCM)　and　ordinary　cement　mortar　(OCM)　with　different　limestone　powder　(LP)　content　were　corroded　by　different　sulfate　solutions　at　5　°C.　The　change　of　compressive　strength　and　compositions　of　corrosion　products　in　mortars　after　different　times　of　corrosion　were　studied.　The　results　show　that　SSCM　presents　9.4∼19　%　lower　strength　loss　and　better　sulfate　resistance　than　OCM.　The　presence　of　Friedel＇s　salt　in　SSCM　contributes　to　a　reduction　in　corrosion　products　like　ettringite,　gypsum,　and　thaumasite,　thereby　minimizing　microstructural　damage　and　mitigating　the　thaumasite　sulfate　attack　(TSA).　All　mortars　containing　LP　suffer　from　TSA　and　significantly　damage　with　17.4∼48.7　%　strength　loss　after　360　days　of　MgSO4　or　Na2SO4　corrosion.　Increasing　the　LP　content　exacerbates　the　TSA　damage　in　SSCM.　This　is　primarily　due　to　the　additional　soluble　carbonate　from　LP　promoting　the　formation　of　gypsum　and　thaumasite,　thereby　worsening　the　microstructure　deterioration　of　SSCM.　Meanwhile,　the　thaumasite　is　not　found　in　SSCM　without　LP　after　corrosion.　In　contrast　to　Na2SO4　corrosion,　the　thaumasite　formation　under　MgSO4　corrosion　mainly　results　from　indirect　reaction.　The　combined　corrosion　effects　of　Mg2+　and　SO42-　lead　to　a　more　significant　increase　in　expansive　products　(thaumasite　and　gypsum)　and　TSA　damage.　The　findings　of　this　study　help　to　advance　the　sulfate　resistance　of　SWSSC　in　marine　environments.　©　2024　Elsevier　Ltd