A study on corrosion protection performance of polypyrole and poly(N-methylpyrole) on the ZnFe coated Carbon Steel

摘要

Due to their potential technological applications, the electrochemical deposition of quality conducting polymer (CP) films has been a main subject in research and development of polymers. There have been many advances in the application of CP films synthesized on the metal surfaces in numerous domains such as electrocatalysis, electrochromic devices, microelectronic devices, modified electrodes, biosensors, and rechargeable batteries. Zinc-alloy electrodeposited coatings and especially can those containing one of the'iron group metals'(e.g. iron, nickel and cobalt) have found important end-uses in various industrial sectors. One of their subgroups, zinc-iron electrodeposited coatings on steel sheets, comprises one of the most promising groups of materials for the automotive industry. The electrodeposited Zn-Fe alloy coating possesses many excellent properties, such as excellent corrosion resistance due to the nature of the zinc-iron phase, excellent paintability, and good welding properties of zinc-iron phase in comparison to the pure zinc [1] and has been considered to be an alternative for pure zinc coating of iron and steel products. This is easily achieved by alloying Zn with more noble metals, mostly with metals of the iron group (Ni, Co and Fe).[2,3] Zinc-iron alloys exist in various phases and their structure and morphology [7] also determine the corrosion resistance of a deposit. Electrochemical polymerization of polypyrole (PPY) and poly(N-methylpyrole) (PNMP) were investigated on Zinc-Iron coated mild steel (MS) electrode. Zinc-Iron layer was deposited galvanostatically, from a proper bath solution. Then, the synthesis of PPy film was achieved in 0.1 M pyrole containing 0.2 M sodium oxalate medium, by using cyclic voltammetry technique. The corrosion performances of zinc-iron coated samples with and without polymer top coats were investigated in 3.5% NaCI solution, by using electrochemical impedance spectroscopy (EIS), open circuit potential-time and anodic polarization curves. The zinc-iron coating behaved like a physical barrier and provided almost some protection to MS against corrosion. But its barrier property diminished significantly with time. The research project was funded by Technical Research Council of Turkey (TUBITAK), Project No:TBAG-HD (110T745).