The work aims to improve the corrosion resistance of Q235 carbon steel by electro-depositing compact PEDOT coatings on it, so as to avoid charge concentration by the good conductivity of PEDOT. EDOT was electropolymerized on a Q235 carbon steel substrate by electrochemical galvanostatic method in sodium dodecyl sulfate (SDS) and lithium perchlorate (LiClO4) solution. Electrochemical interaction between conductive PEDOT coatings and carbon steel substrate as well as the effect laws on corrosion behavior of Q235 carbon steel were investigated by cyclic polarization, open circuit potential monitoring (OCP), electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technology (SVET). At a current density of 5 mA/cm2, the as-deposited PEDOT coatings were the most complete and compact, with agglomerated spherical surface morphology. The coupling current density of the PEDOT/Q235 electrode after 40 h immersion in 3.5wt% NaCl solution was -15 μA/cm2, and the coupling voltage was -715 mV. The multiple cyclic polarization curves of PEDOT/Q235 were almost repeated, showing good electrochemical stability. The OCP and EIS results indicated that the PEDOT coatings passivated the Q235 substrate after 4 days, protecting the substrate. The SVET demonstrated that electron delocalization was formed on the PEDOT coatings, avoiding charge concentration resulting in the reduction of the current density in the scratch zone from 628 μA/cm2 to 23.8 μA/cm2. PEDOT coatings can alleviate the corrosion of Q235 substrate in NaCl solution, which is attributed to the dense structure, the passivation of substrate and the reduction of surface charge concentration.