SECM investigation of electrochemically synthesized polypyrrole from aqueous medium
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The electrochemical behavior of polypyrrole (PPy)-coated carbon steel (CS) was investigated in aqueous NaCl solution by scanning electrochemical microscopy. Oxygen concentration and pH were monitored by placing Pt and Sb microelectrodes, respectively, over the CS sample surfaces while soaking them in corrosion media. The PPy layer provided anodic protection, as well as a physical barrier, against the corrosive effect. The ratio of these properties was dependent on the thickness of the coating. Electrosynthesis of PPy/CS was achieved in an aqueous solution of sodium tartrate and pyrrole using cyclic voltammetric and galvanostatic techniques. The coatings were characterized by X-ray photoelectron spectroscopy and scanning electron microscopy. The doping rate calculated from XPS spectra was estimated at 15 %. The corrosion protective extent of the coating was tested in 3 % NaCl solution using three different techniques: linear polarization, open circuit potential, and electrochemical impedance spectroscopy. PPy offered significant protection against corrosion, with the coating resistance decreasing as immersion time increased.
KeywordsSECM Electropolymerization Polypyrrole Aqueous medium Carbon steel Corrosion
This work was supported by the MESRSFC and CNRST (Morocco) under Grant No PPR/30/2015 and cooperation agreements between Morocco and Hungary (CNRST/NIH) 1091/2014/CNR.
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