The use of polyindole for prevention of copper corrosion

The electrochemical synthesis of polyindole (PIn) film has been achieved on polypyrrole (PPy) coated copper sample. The synthesis of primary PPy coating was carried out from aqueous oxalic acid solution and the synthesis of PIn top film was obtained from 0.15 M LiClO4 solution in acetonitrile. The corrosion performances of PPy/PIn and single PPy coatings have been investigated in 3.5% NaCl solution, by using electrochemical impedance spectroscopy (EIS), anodic polarization curves and open circuit potential–time (Eocp–t) diagrams. It was shown that PPy coating has exhibited physical barrier behaviour against the attack of corrosive environment and reduced the copper corrosion. This coating was also able to exhibit some anodic protection to copper substrate, by catalyzing the formation of protective oxide layer on the surface. It was also shown that PPy/PIn coating gave much better results than the single PPy film. This coating had lower permeability and higher stability that it kept its effective barrier property for longer period, when compared to single PPy. The total porosity value was calculated to be 5.23% for PPy/PIn coating after 200 h of exposure time, while this value was 30.2% for single PPy.