A new smart coating of polyaniline-SiO2 composite for protection of mild steel against corrosion in strong acidic medium

• Published in: Polymer international 2013-08, Vol.62 (8), p.1192-1201
• Main Authors: Kumar S, Anoop, Bhandari, Hema, Sharma, Chandrica, Khatoon, Fehmeeda, Dhawan, Sundeep K
• Format: Article
• Language: English
• Subjects: Applied sciences; Composites; conducting polymer; Corrosion; corrosion inhibitor; Corrosion prevention; Exact sciences and technology; Forms of application and semi-finished materials; Metals. Metallurgy; Polymer industry, paints, wood; Tafel extrapolation method; Technology of polymers
• ISSN: 0959-8103; 1097-0126
• DOI: 10.1002/pi.4406

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 Presence of SiO2 particles entrapped in PANI chain provides the reinforcement to polymer matrix which reduce the degradation of polymer coating on mild steel in acidic condition. PSC coating protect metal by dual mechanism by forming passivating layer as well as acting as a physical barrier.