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Keywords:

  • conducting polymer;
  • composites;
  • corrosion inhibitor;
  • Tafel extrapolation method

Abstract

Organic coating approaches for corrosion protection with inherently conducting polymers have become important because of restriction on the use of heavy metals and chromates in coatings due to their environmental problems. The present work is directed towards the synthesis of polyaniline (PANI) and polyaniline–SiO2 composites (PSCs) by chemical oxidation polymerization in the presence of phosphoric acid and evaluation of synthesized PANI and PSCs for protection of mild steel from corrosion in a strong aggressive medium (i.e. 1.0 mol L–1 HCl). A suitable coating with PSC was formed on mild steel using epoxy resin by the powder coating technique. A comparative study of the corrosion protection efficiency of mild steel coated with PANI and PSC in 1.0 mol L–1 HCl solution was evaluated using the Tafel extrapolation, chrono-amperometry and weight loss methods. The PSC coating showed that a significant reduction in the corrosion current density reflects the better protection of mild steel in an acidic environment. Higher protection efficiency up to 99% was achieved by using PSC-coated mild steel at 6.0 wt% loading of PSC in epoxy resin. The coating performance and corrosion rate of mild steel were investigated by using immersion of polymer-coated mild steel in 1.0 mol L–1 HCl for 60 days and indicated that PSC-coated mild steel showed better performance from corrosion than PANI in an acidic medium.© 2012 Society of Chemical Industry