Enhancing of corrosion protection properties of stainless steel 316L using chemically synthesized thin film poly(pyrrole-co-p-toluidine) coating on SS316L surface in a 3.5 wt.% NaCl medium

• S.A. Lasaddy¹, A.M. Farhan² and A.A. Jabor³

¹ Department of Chemistry, College of Science, University of Baghdad, Jadriya,10011 Baghdad, Iraq
² Department of Chemistry, College of Science for Women, University of Baghdad, Jadriya, 10011 Baghdad, Iraq
³ Ministry of Higher Education and Scientific Research, Jadriya, Baghdad, Iraq

Abstract: Conducting polymers have garnered attention due to their economic feasibility and numerous industrial applications. Polymers possess long-chain carbon bonds that prevent a significant number of metal surfaces from disintegrating when they adsorb them. A barrier between the metal and its surroundings is established by the thin layers that have been adsorbed onto the metal substrate. A coating of thin film poly(pyrrole-co-p-toluidine) was made on stainless steel 316L to protect it better. This was done by chemical oxidative copolymerization with ammonium persulfate as an oxidant in hydrochloric acid water. The chemical structure of the obtained copolymer is characterized by Fourier Transform Infrared Spectroscopy (FTIR) techniques. The copolymer was characterized using XRD, EDS, and the 3-dimensional morphology of the coatings as determined by atomic force microscopy (AFM). To evaluate the protection performance of deposited coatings, their open circuit potential (OCP) values were monitored using a linear polarization process. The corrosion protection efficiency of thin film poly(pyrrole-co-p-toluidine) was assessed through electrochemical measurements of corrosion potential (E_corr), polarization resistance (R_p), corrosion current density (i_corr), and Tafel extrapolation methods in a 3.5 wt.% NaCl medium. The copolymer coatings’ surface morphology was investigated using field emission scanning electron microscopy (FESEM). The results indicate that poly(pyrrole-co-p-toluidine) coating is a potential coating material for preventing corrosion of SS316L in the corrosive medium mentioned above. We determined the protection efficiency by varying the temperature between 298 and 328 K in the absence and presence of (pyrrole/p-toluidine) copolymer coating and computed the values E_a, ∆S⁰, ∆H⁰, and ∆G⁰.

Keywords: corrosion, conducting polymer, electrochemical technique, pyrrole, p-toluidine

Int. J. Corros. Scale Inhib., 2025, 14, no. 1, 227-245
doi: 10.17675/2305-6894-2025-14-1-14

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