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.