Multidimensional Study On The Corrosion Inhibition of Polypyrrole-Chitosan (PPy-CTS) Composites For Carbon Steel In Acid Medium

The acidic corrosion of carbon steel is a great concern, which has caused serious economic losses on a global scale. Therefore, the exploitation of corrosion inhibition strategy for carbon steel and an in-depth study on its mechanism are of vital importance. Here we have developed a mixed type corrosion inhibitor of PPy-CTS, which incorporated the good solubility and adsorption capacity of chitosan (CTS) into the excellent corrosion inhibition performance of polypyrrole (PPy) by in-situ polymerization of pyrrole on CTS. The corrosion inhibition performance of PPy-CTS composites as a potential corrosion inhibitor for Q235 carbon steel in 1 M HCl solution was investigated by electrochemical (potentiodynamic polarization curve and AC impedance spectroscopy) and surface morphological (scanning electron microscopy and water droplet contact angle) characterization. The results revealed that PPy-CTS with the optimal concentration of 250 ppm achieved the highest corrosion inhibition efficiency of 91.1%. Subsequently, the corrosion inhibition mechanism was furtherly studied. Gibbs free energy obtained from the Langmuir isotherm model suggested that the absorption of PPy-CTS corrosion inhibitor on Q235 steel in 1 M HCl solution belonged to a combined type of physisorption and chemisorption, which resulted in the formation of a physical barrier preventing the carbon steel from corrosion. In addition, the conductive polymer PPy of corrosion inhibitor possessed an oxide-film anodic protection for carbon steel. Ultimately, PPy-CTS effectively suppressed the corrosion reaction of carbon steel in harsh acidic environment through the synergistic effect of physical barrier and anodic protection.