Sulphonate doped polyaniline containing coatings for corrosion protection of iron

Polyaniline containing organic coatings are found to protect steel in acid and in neutral media. Since dopants play an important role in the protection ability of polyaniline, a study has been made on the corrosion protection performance of sulphonate doped polyaniline containing vinyl coating in 0.1 N HCl and 3% NaCl by open circuit potential and impedance measurements. The open circuit potential measurements have shown that the coatings with polyaniline maintain the potential in the noble range whereas the coating without polyaniline exhibit potentials in the active range. EIS studies have shown that the sulphonate doped polyaniline is able to protect steel in acid and in neutral media since the impedance values of the coating remained at 1010 Ω cm2 even after 100 days exposure whereas the coatings without polyaniline have lost their protection ability after 50 days and 100 days in the acid and neutral media. FTIR studies have shown that PANI is able to protect by forming iron–PANI complexes beneath the coating along with a passive oxide layer.