Zinc modified polyaniline coating for mild steel protection

Polyaniline (PANi) coating (∼1.1 μm thick) was synthesized electrochemically on mild steel (MS), from 0.1 M aniline containing aqueous oxalic acid solution and using cyclic voltammetry technique. Then, this PANi coating was modified with the deposition of zinc particles from 0.2 M ZnSO4 solution. The electrodeposition of zinc particles (approximately 1 mg/cm2) has been achieved, at the constant potential value of −1.20 V. The corrosion performance of zinc modified PANi coating has been investigated in 3.5% NaCl solution, by using electrochemical impedance spectroscopy and anodic polarisation curves. Also, the corrosion behaviour of single PANi coated MS and bare zinc (Zn) samples have been investigated, for comparison. It was shown that zinc deposition lowered the permeability of polymer film significantly. Also, the zinc particles provided important cathodic protection to MS for considerably long immersion period. The polymer film provided the electrical conductivity between the substrate and zinc particles, this enhanced the cathodic protection efficiency. The corrosion of zinc particles led to formation of very stable corrosion products which improved the barrier property of zinc modified PANi coating system, further.