Formation of poly-2,5-dimethoxyaniline on steels

Stable films of poly-2,5-dimethoxyaniline were grown on 304 stainless steel by electrochemical polymerisation in an oxalic acid electrolyte. The conducting polymer was also formed electrochemically on mild steel, but the film was unstable and readily peeled off when cycled in a monomer-free electrolyte. Cyclic voltammetry and in situ Raman spectroscopy showed that the poly-2,5-dimethoxyaniline on 304 stainless steel existed in a partially oxidized state only over a narrow range from around 200 to 400 mV (SCE). Corrosion potential tests in 0.5 M HCl were marked by fluctuations in the potential from −150 to +250 mV (SCE) over a period of several days as regions of oxidized polymer reached and passivated the steel substrate, in a similar manner as has been observed for polyaniline.