Development of anti-corrosion and hydrophobicity of a nanostructured Ce-La film via the PDA post-treatment modification

The Ce-La film has been created to improve the adhesion of the organic coatings with the metal surface. However, the development of cracks coincides with the formation of the Ce-La conversion coating. In addition, the high hydrophilicity of the Ce-La conversion coating adversely affects its adherence properties. In this study, poly-dopamine (PDA) in two forms namely PDA-A and PDA-B were employed as post-treatment layers to enhance the adhesion and corrosion resistance of the Ce-La film on Q235 carbon steel. The microstructure, wettability, and corrosion resistance were investigated. The results revealed that the PDA healed the cracks and increased the surface roughness and thickness of the Ce-La conversion coating. Moreover, the Ce-La film becomes more hydrophobic, and the contact angle increased from 6.509 degrees to 61.745 degrees and 85.009 degrees after applying the PDAA and PDA-B layers, respectively. The application of the PDA-B post-treatment layer significantly improved the overall corrosion resistance (Rt) of Ce-La conversion coating, increasing the Rt from 1180.6 to 1299.6 ohm.cm2 and decreasing the corrosion current density (icorr) from 2.466 to 1.652 mu A/cm2. These findings demonstrate that applying PDA can improve both the adhesion and corrosion resistance of the Ce-La conversion coating.