Steel protection of two composite coatings: Polythiophene with ash or MCM-41 particles containing iron(III) nitrate as inhibitor in chloride media

•Two composite corrosion coatings of mild steel were evaluated in chloride media.•Composite coatings studied were P1 polymer and containers of iron nitrate inhibitor.•P1 polymer was a polythiophene derivative and containers were ashes and MCM-41.•Electrochemical noise measurements was used to evaluate the corrosion protection.•Good performance was obtained with the two composite corrosion coatings.

This work presents the evaluation of two corrosion protection coatings applied to mild steel which was exposed to a 3% chloride solution at different immersion times. The coatings were processed composites (P1 polymer-ashes and P1 polymer-MCM-41) using iron (III) nitrate as a corrosion inhibitor in their matrix. P1 polymer is a polythiophene derivative of 3-HT and (S)-(−)-1-(4-nitrophenyl)pyrrolidin-2-yl)methyl-2-(thiophen-3-yl)acetate. Ashes and MCM-41 (a type of mesoporous silica material) were used as containers of the iron (III) nitrate inhibitor. The coatings were characterized using nuclear magnetic resonance (NMR), Fourier Transform Infrared (FT-IR) and scanning electron microscopy (SEM). Polarization curves were used to determine the optimal concentration of inhibitor, and electrochemical noise measurements (ENM) to evaluate the corrosion protection performance. The electrochemical noise analysis (ENA) included: statistical (standard deviation) and Fast Fourier Transform (FFT) analysis to obtain the impedance spectrum and to evaluate the corrosion coating system’s behavior. Good performance was obtained with the two anti-corrosion coatings that were applied and their inhibitor containers.

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