The self-assembled monolayers (SAMs) of 2,5-bis(4-pyridyl)− 1,3,4-oxadiazole (4-POX) were formed on carbon steel (CS) surface to improve the corrosion resistance of the substrate in 1 M HCl medium. The structural characterisations of 4-POX/SAMs films were performed by using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), and contact angle measurements. The protection ability of SAM films against CS-substrate corrosion in 1 M HCl was studied using potentiodynamic polarization and AC impedance techniques. FTIR and XPS results showed that the 4-POX molecules adsorbed on the CS surface, and the contact angle values on the modified surface supported the formation of hydrophobic 4-POX/SAMs. The results of electrochemical measurements indicated, when the self-assembling time increased, the corrosion resistance od 4-POX/SAMs film enhaced, reaching a maximum protection efficiency value of 94.6% for 6 h of self-assembly. Different kinds of surface pre-treatments (amorphous phosphatation (Pa), APTES (PAPTES), and N2 plasma (PN2)) of CS-substrate were then applied in order to improve the corrosion resistance of SAM process.