Protective properties of hexacyanoferrate containing polypyrrole films on stainless steel

The protective properties of polypyrrole coatings containing hexacyanoferrate anions are presented. The composite coatings were electrodeposited galvanostatically on stainless steel from the aqueous solutions containing pyrrole monomer and potassium hexacyanoferrate(II) together with traces (10 μmol dm−3) of free CN− ions. The protective properties of the resulting coatings were investigated in the highly aggressive medium of 0.1 mol dm−3 HCl and 0.4 mol dm−3 NaCl. Diagnostic experiments included measurements of open circuit potential with time of exposure, chronoamperometric (current-time) examination of the steel samples at a selected constant potential of 0.5 V and potentiodynamic measurements. To get insight into the dynamics of the steel dissolution at open circuit potential and at the selected anodic potential, changes of concentrations of iron and chromium in the test solution as a function of exposure time were determined using atomic absorption spectrometry. Morphology of the composite film was examined using scanning electron microscopy.