The Effect of Electrolyte Composition on the Corrosion Protection Performance of PANI and PANI/CeO2 Composite Coatings

The electrolytic composition plays an important role in the structure and corrosion protection performance of electro-polymerized coating. In the present work, oxalic acid, hydrochloric acid, sulfuric acid, phosphoric acid and benzoic acid were utilized as electrodeposition electrolytes to prepare a PANI coating. The PANI coating deposited in benzoic acid showed a compact and uniform structure with an adhesion grade of 0. Electrochemical tests revealed that the benzoic acid-doped PANI coating exhibited the smallest value of corrosion current density of 2.571 μA·cm−2 and the largest inhibition efficiency of 92.6% among the investigated acidic electrolytes. Moreover, the influence of co-electrodeposition conditions, including cerium nitrate concentration, ammonium acetate concentration and electrolyte pH value on the corrosion protection performance of co-electrodeposited PANI/CeO2 was investigated and the optimal co-electrodeposition condition was found to be 0.3 mol/L aniline, 0.04 mol/L benzoic acid, 0.10 mol/L cerium nitrate, 0.10 mol/L ammonium acetate and pH of 5.5, under which condition the corrosion current density was decreased to 0.199 μA·cm−2 and the inhibition efficiency reached 99.4%.