Abstract: The polarization behavior of rebar with mill scale and stains was investigated in simulated solutions with and without chlorions． The results showed that the hot-rolled rebar without and with stains could be passivated in strong alkali solutions without chloride，but the latter usually needs higher passive current density． Dense mill scale had some protective function when pH = 10 ～ 12. 5，but became unstable when pH13. 5． The rebar with dense mill scale and without stains also could be passivated in strong alkali solutions with some chlorides，but the rusted one kept being in active corrosion state．