An easy route for preparation of carboxylic acid and urea functional block copolymer as corrosion inhibitor

Abstract

A novel POEGMA-b-(PMEEU-co-PMAA) (poly(oligo(ethylene glycol) methacrylate)-b-poly((methacrylamidoethyl) ethylene urea)-co-poly(methacrylic acid) block copolymer has been synthesized by RAFT polymerization as a corrosion inhibitor. Structural characterization of the block copolymer was done by FTIR, 13C NMR and 1H NMR spectroscopic techniques. The carboxylic acid and cyclic urea units on the block copolymer exert a synergistic effect on corrosion inhibition through chelating of the metal ions or adsorption to the metal surface. Corrosion inhibition of SAE 1012 carbon steel in a 1 M HCl medium has been investigated in the presence of 5 mM polymer using both experimental (electrochemical impedance spectroscopy, Tafel polarization (TP), weight loss) and theoretical approaches. Also, SAE 1012 carbon steel surface morphology changes were followed by energy dispersive X-ray spectroscopy and scanning electron microscopy. Electrochemical techniques indicated that the presence of PMEEU-co-PMAA segments of the polymer in the acid solution inhibits corrosion of SAE 1012 carbon steel. The inhibition efficiency of the polymer was found to be about 85%. According to TP studies, PMEEU-co-PMAA segment acts as a mixed type corrosion inhibitor. The adsorption of PMEEU-co-PMAA molecules onto the metal surface follows Langmuir adsorption isotherm. The K ads value calculated from the equilibrium constant of the adsorption process reflects a strong interaction. SEM and EDAX studies provide evidence of PMEEU-co-PMAA adsorption on the metal surface.