Corrosion Processes Controlled by Phosphonic Acid Nano-layers

Abstract

Self assembled monolayers (SAM) formed by fluoro-phosphonic and undecenyl-phosphonic acids on carbon steel surfaces as anticorrosive nanocoatings were investigated. The anticorrosive efficacy of these SAM layers was followed by atomic force microscopy, when the change in the surface morphology caused by layer deposition and corrosion processes was monitored. The corrosion process was determined by electrochemical potentiodynamic polarization and cyclic voltammetry. Results showed that both chemicals produced good protection against corrosion as anodic inhibitors specially with increasing the time of layer formation which results in a more compact molecular film. According to the AFM images, the fluoro-phosphonic acid self-assembled molecular layer can control the general as well as the pitting corrosion, but the SAM layers of the undecenyl-phosphonic acid cannot inhibit the pitting corrosion. The AFM measurements confirmed the electrochemical results.