Electrodeposition of polypyrrole-titanate nanotube composites coatings and their corrosion resistance

Polypyrrole (PPy) films (2 μm) containing titanate nanotubes (TiNT) were deposited from 0.5 mol dm⁻³ pyrrole (Py) and 1 g dm⁻³ of TiNT in 0.1 mol dm⁻³ aqueous oxalic acid on 904 L stainless steel (SS) 0.1 mm thickness at 298 K. Electron microscopy showed that the nanotubes were adsorbed on the PPy surface and uniformly dispersed in the polymer matrix. The PPy/TiNT composite contained <10 wt.% titanates which showed an increase of 53% hardness compared with polypyrrole alone. The TiNT provide nucleation centres to catalyze the polymerization of pyrrole and can adsorb up to 240 mg g⁻¹ of the monomer. The corrosion rates for SS, SS/PPy and SS/PPy/TiTN composites, evaluated by linear sweep voltammetry and open-circuit potential measurements in 3% w/v NaCl, were 1.61, 0.008 and 0.004 mg dm⁻² day⁻¹, respectively, indicating that corrosion rates of stainless steel decreased by up to three orders of magnitude in the presence of the composite films.