[Objective]　In　the　context　of　the　“dual　carbon”　goals,　liquid　ammonia　is　anticipated　to　serve　as　an　efficient　and　safe　hydrogen　storage　carrier.　However,　during　long-distance　pipeline　transportation　of　liquid　ammonia,　stress　corrosion　cracking　may　occur　in　the　pipes,　leading　to　leakage　and　compromising　the　intrinsic　safety　of　the　pipeline　operation.　Therefore,　it　is　crucial　to　investigate　the　susceptibility　of　pipeline　steel　to　stress　corrosion　from　liquid　ammonia　to　ensure　pipeline　safety.　[Methods]　To　analyze　the　stress　corrosion　behavior　of　X80　pipeline　steel　in　a　liquid　ammonia　environment　with　impurities,　C-ring　stress　corrosion　tests　were　conducted　under　varying　levels　of　water,　oxygen,　and　stress.　The　coupled　effects　of　these　impurities　and　stress　on　the　corrosion　behavior　were　quantitatively　assessed　using　weight　loss　and　control　variable　methods.　This　study　clarified　the　evolution　and　internal　mechanisms　of　liquid　ammonia　stress　corrosion　in　pipeline　steel　based　on　corrosion　rates,　micro-morphology,　and　corrosion　products.　[Results]　In　anhydrous　liquid　ammonia　environment,　the　corrosion　rate　of　pipeline　steel　increased　with　higher　oxygen　content　and　rose　sharply　with　increased　stress.　When　water　with　a　mass　fraction　of　0.20％　was　added　to　oxygen-containing　liquid　ammonia,　the　corrosion　rates　of　pipeline　steel　decreased　within　the　studied　range　of　oxygen　concentrations.　The　coupled　effect　of　oxygen　concentration　and　stress　can　lead　to　the　formation　of　corrosion　products　on　the　surface　of　pipeline　steel.　At　100％　of　yield　strength,　corrosion　products　appeared　as　granular　deposits,　and　cracks　began　to　initiate　and　propagate.　As　stress　increased　to　125％　and　150％　of　yield　strength,　additional　cracks　formed　on　the　surface　of　the　pipeline　steel,　partially　connecting　with　one　another,　while　the　corrosion　morphology　shifted　to　cementitious　deposits　accompanied　by　crack　formation.　When　adding　water　with　mass　fractions　of　0.20％　and　1.00％,　respectively,　only　a　few　microcracks　and　corrosion　products　appeared　on　the　surface　of　pipeline　steel,　even　under　high　stress,　indicating　that　a　certain　amount　of　water　can　inhibit　liquid　ammonia　stress　corrosion　cracking　in　pipeline　steel.　[Conclusion]　During　the　design,　construction,　and　operation　of　liquid　ammonia　pipelines,　it　is　essential　to　consider　the　influence　of　factors　such　as　the　mixing　of　oxygen　impurity,　the　high　stress　resistance　of　pipes,　and　residual　strain　from　construction　on　liquid　ammonia　stress　corrosion　cracking.　If　necessary,　adding　a　small　amount　of　water　can　mitigate　the　risk　of　corrosion　and　enhance　the　safety　of　high-grade　steel　pipelines.　©　2025　Editorial　Office　of　Oil　and　Gas　Storage　and　Transportation.　All　rights　reserved.