Novel coumarin-buta-1,3-diene conjugated donor–acceptor systems as corrosion inhibitors for mild steel in 1.0 M HCl: Synthesis, electrochemical, computational and SRB biological resistivity.

[Display omitted] • Three novel cyano coumarin compound were synthesized and approved by FTIR, 1H NMR and Mass spectroscopy. • The synthesized inhibitors obeyed Langmuir adsorption mode with a chemical adsorption. • The metal was protected by the creation of a protective layer on the surface, according to SEM, EDX, and UV data. • The corrosion related to SRB can be controlled by the current organic coumarin inhibitors. New synthesized coumarin-buta-1, 3-diene conjugated dyes having donor–acceptor structure were prepared. The characterization of the synthesized dyes was approved by using IR, 1H NMR and Mass fragmentation analysis. The adsorption properties for the synthesized coumarin compounds were determined by experimental and theoretical methods. The corrosion inhibition effect of the synthesized coumarin dyes against steel in acid environment was investigated by plasma atomic emission spectrometer, weight loss and electrochemical methods. The highest corrosion efficiency was 97.62 % resulted from potentiodynamic polarization technique at the highest concentration for Dye 2 inhibitor. The adsorption mechanism of the inhibitors was investigated and thermodynamic parameters were calculated. The surface protection examination was carried out using scanning electron microscopy and the formation of the complex on the surface was approved using Energy dispersive X-ray spectroscopy and UV– visible spectroscopy. The quantum chemical calculations were used to confirm the donor–acceptor system of the synthesized coumarin compounds. The biological activity effect versus sulfate reducing bacteria was confirmed. The experimental and theoretical results assure that these current synthesized dyes have a good ability to protect the steel from corrosion by forming a protective layer on the surface. [ABSTRACT FROM AUTHOR]