Electrochemical deposition of a carbon nanotube-poly(o-phenylenediamine) composite on a stainless steel surface

Electrodeposition of a nano-composite made of oxidized carbon nanotubes (CNTs) and a conductive polymer such as poly(o-phenylenediamine) (PoPD) on a stainless steel surface from aqueous solution was carried out by cyclic voltammetry. The presence of the CNTs enhanced the deposition of the PoPD and this enhancement was more significant in the presence of single walled carbon nanotubes (sCNT) by comparison to multi-walled carbon nanotubes (mCNT). Scanning electron microscope images indicated the incorporation of the CNTs in the PoPD layer. The nano-composite layer as well as the pure PoPD layer keeps the stainless steel in a passive state in acidic solution. The oxide film underneath the nano-composite layer is unique and showed high corrosion resistance in concentrated chloride solutions, which was confirmed by the presence of high contents of iron and chromium components. These findings suggest that the CNTs indirectly assist the passivation of the stainless steel by catalyic oxygen reduction and polymer oxidation process.