The investigation of effect of polyaniline coating synthezed as electrochemical and the investigaton of the effect of poly aniline coating on nickel on 304 steel corrosion behaviour

The aim of this study is to determine the corrosion characteristics of 304 steel by the methods of Tafel extrapolation, linear polarization and electrochemical impedance spectroscopy (EIS). The polyaniline (PANI), which is a conductive polymer, is synthesized on the steel surface by the way of electrochemical cyclic voltammetry method. The steel surface is covered with nickel as electrochemical Watt?s bath. Additionally, PANI is synthesized on the steel electrode covered with nickel by the method of electrochemical cyclic voltammetry method. The effect of single and double coats of steel on corrosion resistance is examined in 3.5 % NaCl, 1 N NaOH and 1 N HCl solutions for the time zone of 0, 48, 120 and 168 hours. The surface morphology of steel, which is uncovered, is examined by SEM-EDX and the PANI one is also examined in the same way. And the one covered with Ni + PANI is examined in the same way too. The synthesized polyaniline on the surface is analyzed by FTIR spectrum. The film thickness occurred on the surface is measured by optic micrometer. Double coatings (Ni + PANI) has showed better corrosion resistance than single coating (PANI). The cyclic voltammograms obtained in 0,3 M oxalic acid + 0,1 M aniline solution shows that there is PANI coat on steel surface. The reaction occurrence of PANI is autocatalytic. PANI supports the oxide formation on the steel surface. Ni+PANI coatings in 1 N NaOH and 1 N HCl solutions has showed better corrosion resistance than PANI coating. On the other hand, PANI coating in 3.5% NaCl solution has revealed better corrosion resistance than Ni+PANI coatings for 48 and 120 hours. However, Ni+PANI coatings has showed better resistance than PANI coating for 0 and 168 hours. The corrosion current of the steel covered with Ni+PANI in 1 N HCl and 1 N NaOH solutions is lower than the corrosion current of PANI coating. The corrosion current in the steel covered with PANI in 1 N NaOH solution has decreased in the course of time. SEM-EDX analyses have showed that the surface covered with Ni+PANI is more homogenous and compact. This result is also convenient with the electrochemical experiment results.