Stainless　steels　typically　feature　high　toughness　and　good　corrosion　resistance.　However,　pitting　corrosion　can　easily　occur　on　stainless　steel　and　the　passivation　film　tends　to　be　vulnerable　under　pressure　or　in　brine　environments.　Metal　corrosion　is　a　long-standing　challenge　for　the　steel　industry,　forging　a　path　to　net-zero.　Herein,　by　successive　growth　of　a　series　of　quantum　confined　nanocrystals　such　as　quantum　dots　and　nanorods　with　gradient　band　energy　level　alignment,　high-performance　photoelectrochemical　cathodic　protection　for　steel　is　demonstrated　with　remarkable　mechanical　and　electrochemical　stability.　Under　simulated　solar　light　illumination,　effective　photoinduced　protection　can　be　realized　for　304　stainless　steel　which　enables　long-term　corrosion　resistance　in　a　3.5　wt%　NaCl　solution.　Unique　nanotree-like　structures　and　the　quaternary　material　combination　can　store　excess　charges　and　release　them　gradually,　enabling　time-delay　protection　for　metals　after　light　excitation.　Various　promising　functionalities　as　unique　photoelectrodes　can　be　envisioned　arising　from　the　proposed　3D　nanotree　morphology.　©　2022　Elsevier　B.V.