The effect of polypyrrole and nickel plus polypyrrole coatings on corrosion behaviour AISI 304 stainless steel

Polypyrrole (PPy) and nickel + PPy (Ni + PPy) coatings have been occured on AISI 304 stainless steel (304 SS) surface by cyclic voltammetry technique in aqueous oxalic acid solutions and as the supporting electrolytes was used saccharin and NaNO3. Corrosion behavior of the PPy and Ni + PPy coated 304 SS electrodes was investigated using linear anodic polarization, Tafel extrapolation and electrochemical impedance spectroscopy (EIS) techniques in various aqueous solutions. The polypyrrole coated samples were characterized by scanning electron microscope (SEM) and Fourier Transform Infrared spectroscopy (FTIR). SEM analysis showed that PPy structure depends closely on the electrochemical conditions. Additionally, it is seen from FTIR analysis, characteristic polypyrrole absorption bands have occurred in all the coated surfaces. Tafel analyses and open-circuit potential datas revealed that the PPy and Ni + PPy coatings effectively protect the steel from corrosion in H2SO4 and NaOH solutions. However, the corrosion protection properties were reduced with immersion time. Ni + PPy coatings more effectively protects the steel from corrosion than polypyrrole.