35CrMn is a kind of light rail steel.The corrosion of 35CrMn and Q235 steel under simulated acid rain were investigated through polarization curves,electrochemical impedance spectrum,and X-ray diffraction.Especially the effects of pH value of acid rain and immersion time on the corrosion of these two steels were studied.It was found that the corrosion current and corrosion rate of 35CrMn and Q235 steel increased with the decreasing of pH value of simulated acid rain,correspondingly the corrosion potential of 35CrMn steel became more negative.Meanwhile,the impedance of corrosion product became higher and corrosion rate was lowered with the increasing of immersion time,which indicated that the corrosion product was some protective to the steel base.The results illuminated that the corrosion rate of 35CrMn steel was obviously lower than that of Q235 steel.The X-ray diffraction analysis showed that the phase components of the rust layer on the 35CrMn steel and Q235 steel was similar,but α-FeOOH existed in the rust of 35CrMn steel was more than that of Q235 steel.The α-FeOOH could prevent the based steel from the corrosive anions permeating.And this might be the cause of the difference of corrosion behavior between 35CrMn steel and Q235 steel.