Polypyrrole films on stainless steel

Polypyrrole (PPy) films have been deposited on stainless steel substrates from two different solutions; 0.15 M LiClO4 in acetonitrile (ACN-LiClO4) and 0.3 M oxalic acid in water. For this aim cyclic voltammetry technique was used and approximately 1.7 μm thick PPy coating was obtained, applying the same potential range for the film growth in both solutions. The corrosion behaviour of coated and uncoated samples was investigated in 3.5% NaCl solution, using ac impedance spectroscopy and anodic polarisation curves. It was shown that the film obtained from ACN-LiClO4 had less porous structure and higher stability than that obtained from aqueous oxalic acid solution. The ac impedance results showed that both coatings exhibited important anodic protection behaviour and enhanced the self passivation of steel with protective oxide film.