Influence of sulfonic acid doping during polypyrrole electrodeposition on the corrosion protection for AA2024-T3

The electrodeposition of polypyrrole on AA2024-T3 was prepared by applying a constant potential via three different dopants including sulfuric acid (SA), p-toluenesulfonic acid (pTSA), and 2-naphthalenesulfonic acid (2NS). The polypyrrole coating was characterized by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The anti-corrosion behavior was examined by Tafel curves to find the optimized concentration and deposition time for each dopant. Polypyrrole was successfully electrodeposited on AA2024-T3 with pTSA and 2NS dopants, which exhibited better corrosion protection compared with bare AA2024-T3. In addition, a conventional coating was applied with spray paint considered as a topcoat to further investigate the protection efficiency of the polypyrrole. The 2NS-doped polypyrrole exhibited a good protection efficiency of 99.99%. The results demonstrated that the chemical structure of the dopant influences the corrosion protection where the corrosion potential has positively increased with the extended electrodeposition time. Topcoat with spray paint working as a surface barrier can protect the polypyrrole coating and enlarge the protection time.