Anti-corrosion behavior of copolymer (thiophene-co-pyrrole) coating for carbon steel alloy at different deposition times in 3.5% NaCl solution

• H.M. Raheem¹, T.A. Salman¹ and A.A. Jabor²

¹ Chemistry Department, College of Sciences, Al-Nahrain University, Jadriya, Baghdad, Iraq
² Ministry of high education and scientific research, Scientific research commission, Center for Industrial Applications and Materials Technology, Jadriya, Baghdad, Iraq

Abstract: In this study, the electrophoresis deposition (EPD) method was employed for depositing the prepared poly(thiophene-co-pyrrole) conducting copolymer onto carbon steel alloy from a copolymer acetone suspension at various deposition times of 30, 45, and 60 minutes for corrosion protection application. FeCl3 was used as the single reagent system in chemical oxidative polymerization to form the copolymer. This copolymer significantly increases the polymeric coating’s resistance to corrosion by preventing corrosive ions from penetrating the carbon steel alloy. The prepared copolymer was distinguished by measuring the X-ray diffraction, Fourier transform infrared (FT-IR) spectroscopy, and thermal gravimetric analysis (TGA). To examine the copolymer’s morphology, field emission scanning electron microscopy (FE-SEM) was used with elemental analysis (EDS) for the coating sample, and atomic force microscopy (AFM) to detect the topography of the coating and the diameter of particles on the alloy surface. The findings revealed that the electrophoretic deposition (EPD) method effectively applied a copolymer layer onto the carbon steel alloy, yielding a uniform and smooth coating. The applied voltage used in the coating process is (0.5–15) volts. The performance against corrosion of poly(thio-co-py) copolymer coated carbon steel alloy has been investigated by potentiodynamic polarization technique, in a 3.5% NaCl solution within the 293 K to 333 K temperature range. The findings demonstrated that the coating behaves as an anodic-type inhibitor for all temperatures. Protection efficiencies data were increased as the deposition time of coating increased, and the efficiency of these protective coatings exceeds 84.81%, with the highest performance observed at a deposition time of 1 hour at 293 K.

Keywords: electrophoretic deposition, conducting copolymer, coating, carbon steel, corrosion protection, saline medium

Int. J. Corros. Scale Inhib., 2025, 14, no. 2, 876-893
doi: 10.17675/2305-6894-2025-14-2-23

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