The　effect　of　precipitate　size　and　state　on　stress　corrosion　property　of　7050　aluminum　alloy　has　been　investigated　for　the　first　time.　The　results　suggest　that　7050　aluminum　alloy　with　fine　precipitates　in　matrix　and　discontinuous　copper-rich　precipitates　at　grain　boundary　exhibits　excellent　stress　corrosion　resistance.　The　different　precipitates　in　matrix　lead　to　electrochemical　heterogeneity　and　different　corrosion　susceptibility,　due　to　the　different　coherence　with　matrix　and　alloy　element　matrix　solute　content.　The　discontinuous　grain　boundary　precipitates　can　hinder　corrosion　cavities　connecting　into　a　continuous　crack,　and　copper-rich　grain　boundary　precipitates　can　retard　hydrogen　embrittlement,　during　the　stress　corrosion　process.　Furthermore,　the　in-situ　electrochemical　impedance　spectroscopy　(EIS)　in　real　time　suggests　that　precipitate　state　has　obvious　influence　on　passivation　during　the　stress　corrosion　process.　Fine　nanoscale　precipitates　in　matrix　are　beneficial　to　maintaining　continuous　passivation,　and　the　copper-rich　grain　boundary　precipitate　is　beneficial　to　repassivation.　(C)　2016　Elsevier　Inc.　All　rights　reserved.