Characterization and corrosion protection properties of composite material (PANI+TiO2) coatings on A304 stainless steel

This work presents the corrosion protection behavior of A304 stainless steel in an acidic medium by using coatings based on polyaniline+TiO2 composite material. The influence of parameters such as concentration of aniline, TiO2 content, and pH of the solution were investigated. The coatings which had been deposited by cyclic voltammetry on substrates of A304 steel were then characterized by electrochemical impedance spectroscopy. The cyclic voltammograms showed three redox couples characteristic of the different oxidation and reduction states of the produced polymer. PANI+TiO2 composite material was observed to exhibit higher corrosion resistance and better properties. The effectiveness of coatings in preventing corrosion was tested by potentiodynamic polarization studies and scanning electron microscopy was used to characterize the morphology of the coatings. The results showed that PANI+TiO2 coatings offer good anticorrosion protection to steel in 1 M H2SO4 solutions. The micrograph taken at the coatings surface showed that (PANI+TiO2)/A304 composite was uniform in nature and TiO2 particles were uniformly covered by PANI. After immersion into a corrosive solution for 45 min, no aggressive effect was observed and the coating films were still present. Moreover, the formation of PANI+TiO2 composite was also confirmed by EDX. Furthermore, it was found that the presence of a low amount of TiO2 in PANI coatings afforded the best protection due to the formation of a coating layer on the metallic surface which behaved like a physical barrier against the aggressive medium attack.