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

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.