The Open Corrosion Journal

2011, 4 : 18-26
Published online 2011 March 22. DOI: 10.2174/1876503301104010018
Publisher ID: TOCORRJ-4-18

The Protection Performance of Polypyrrole Coating Doped with Different Counter Anions for the Corrosion of NiTi Alloy

Kai Qi , Zhenyu Chen , Guoan Zhang and Xingpeng Guo
School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Hubei Key Laboratory of Materials Chemistry and Service Failure, Wuhan 430074, PR China

ABSTRACT

The electrochemical corrosion behavior of NiTi alloy electrodeposited conductive polypyrrole (PPy) coatings doped with small size sulfate (SO42-), medium size para-toluene sulfonate (pTS-) and large size dodecylbenzene sulfonate (DBS-) counter anions has been studied by electrochemical measurements and surface analysis. It is demonstrated that PPy coatings inhibit the corrosion of NiTi substrate in chloride solution by shifting the corrosion potential and pitting potential positively and increasing the impedance of corrosion process. The protective performance of PPy coatings for NiTi alloy is in the order: PPy/pTS < PPy/SO4 < PPy/DBS. The protective performance of the doped PPy coatings for NiTi alloy is related to their anions exchange abilities. The worse anion exchange ability PPy coating has, the better protective performance. The increase of solution pH increases the corrosion rate of the coated NiTi substrate.

Keywords:

NiTi alloy, polypyrrole coating, size of doping anion, corrosion.