Electrochemical synthesis of poly(N-methylpyrrole) on stainless steel in the presence of sodium dodecylsulfate and investigation of its corrosion protection performance

In this study, poly (N-methylpyrrole)-dodecylsulfate (PNMPy-DS) coating electrochemically was prepared by potentiodynamic method on an AISI 304 stainless steel in oxalic acid solution containing sodium dodecylsulfate (SDS). For this reason, firstly AISI 304 stainless steel electrode was passivated in 0,3 mol L−1 oxalic acid solution, then the polymer coating was synthesized with cyclic voltammetry method on this surface after N-methylpyrrole and SDS adding to this solution. The effects of electrochemical synthesis parameters, such as upper potential (0,8 V; 0,9 V; 1,0 V), scan rate (10 mV s−1, 25 mV s−1, 50 mV s−1, 100 mV s−1) and cycle number (5, 10, 20, 50), on the protective behaviors of PNMPy-DS films were investigated and the optimum synthesis conditions were determined. PNMPy-DS coating was characterized by cyclic voltammetry, FT-IR spectroscopy and SEM methods. Corrosion protection behavior of this polymer-coated steel was investigated in 0,5 mol L−1 HCl solution by potentiodynamic polarization and EIS methods. Furthermore, the effects of the passivation process and SDS were examined on the corrosion protection behavior of the polymer coating. The best corrosion protective behavior was obtained by the polymer coating prepared in the presence of SDS on passivated electrode surface. The results showed that the PNMPy-DS coating provides effective protection for the stainless steel against to corrosion due to the fact that the large negatively charged dodecylsulfate dopant in the polymer structure electrostatically repels corrosive chloride ions and delays their access to metal surface.