Water-based acrylic copolymer as an environmentfriendly corrosion inhibitor onto carbon steel in 1 M H2SO4 in static and dynamic conditions

Abstract

Background: The green corrosion inhibitors serve recently as a source of environmental friendly materials in the corrosive media. In present study, corrosion inhibitive performance of a new environment-friendly acrylic copolymer (methyl methacrylate/butyl acrylate/acrylic acid) on the mild steel in 1 M H2SO4 solution in the quiescence and hydrodynamic conditions was investigated. Methods: Corrosion studies was performed by potentiodynamic polarization, electrochemical impedance Spectroscopy (EIS), quantum chemical calculations, optical microscopy and rotating disk electrode (RDE) techniques. Results: Polarization experiment showed that the inhibition efficiency increased with increasing the inhibitor concentration and the inhibitor acted as mixed–type controls predominantly cathodic reaction in whole conditions. The thermodynamic calculations showed that the inhibitor obeys Langmuir adsorption isotherm. The increase in the inhibitor concentration and immersion time had a positive effect on inhibition efficiency while temperature had a negative effect. In the hydrodynamic conditions in 600 ppm (optimum inhibitor concentration), the most efficiency was at 1500 rpm rotation speed which was attributed to the enhance mass transfer of inhibitor to the metal surface and then decreased through the high shear stress. Theoretical Density function theory (DFT) calculations reveal that the unshared pairs of electrons on oxygen atoms in functional groups such as OH, C=O and also π electrons in double bonds in structures of three monomers are suitable centers to adsorb. Finally, optical images showed that the presence of inhibitor decreased the corrosion attack sites on the surface. Conclusions: Acrylic copolymer (methyl methacrylate/butyl acrylate/acrylic acid was synthesized and it is suitable inhibitor for mild steel in 1M H2SO4 solution in static conditions and increasing its concentration increases its inhibition efficiency.