A bilayer coating was prepared by electrodepositing a polybithiophene (PBT) film on the top of square wave passivated 304 stainless steel (304SS). The structure of the PBT layer was characterized by FTIR spectroscopy and suggested to be composed of α–α coupling thiophene units. The electrochemical properties of the coating were investigated in 1 mol/L sulfuric acid solution by anodic polarization and electrochemical impedance spectroscopy measurements. The results indicated that the bilayer could provide an effective barrier and maintain the metal substrate in a passive state during the immersion time. The interfacial shear strength of the polythiophene film on untreated and passivated 304SS were 0.81 and 5.1 MPa, respectively. The better result given by treated one may be due to PBT growing within the pores formed on the square wave passivated 304SS.