Corrosion inhibition of polyaniline and poly( o-methoxyaniline) on stainless steels

• Published in: Synthetic metals 2002-11, Vol.131 (1), p.99-109
• Main Authors: Kilmartin, Paul A, Trier, Lissa, Wright, Graham A
• Format: Article
• Language: English
• Subjects: Applied sciences; Conducting polymer; Corrosion; Corrosion prevention; Exact sciences and technology; Forms of application and semi-finished materials; Metals. Metallurgy; Poly( o-methoxyaniline); Polyaniline; Polymer industry, paints, wood; Sheets and films; Technology of polymers
• ISSN: 0379-6779; 1879-3290
• DOI: 10.1016/S0379-6779(02)00178-9

Polyaniline films were grown by electrochemical deposition on 316 and 304 stainless steels and their corrosion performance monitored by following the open circuit potentials in acidic solutions. Poly( o-methoxyaniline) was successfully polymerised on stainless steel electrodes, as shown by cyclic voltammetry and impedance spectroscopy, and provided corrosion inhibition in a similar manner to polyaniline. In 0.5 M H 2SO 4 the potential climbed to over 0.4 V (SHE), to values typical of the partially oxidised form of the polymer and of the metal substrate in a passive state with low rates of corrosion. In 0.5 M HCl, the steels were maintained in a passive state for some hours to days (lasting longer with a thicker polymer film), prior to a drop in potential to −0.15 V after the onset of pitting corrosion. The fluctuations of potential seen in 0.5 M HCl are explained by regions of the oxidised polyaniline, produced by dissolved O 2, reaching the metal and causing an increase in the potential, and by pits formed at higher potentials rapidly reducing an already oxidised film leading to a drop in the potential.