Investigation the inhibitory action of novel diquaternary Schiff dibases on the acid dissolution of carbon steel in 1 M hydrochloric acid solution

Corrosion inhibition of four diquaternary N,N-pentane-2,4-diylidenedipyridin-4-amine (NDSI), N,N-(3-benzylidenepentane-2,4-diylidene)dipyridin-4-amine (NBDSI), N,N-[3-(4-methoxybenzylidene)pentane-2,4-diylidene]dipyridin-4-amine (NMDSI) and N,N-[3-(4-chlorobenzylidene)pentane-2,4-diylidene]dipyridin-4-amine (NCDSI) on carbon steel was investigated by gravimetric measurements, polarisation and electrochemical impedance spectroscopy (EIS). The effect of concentration and immersion time was studied. The results show that the inhibitors are good inhibitor for corrosion reaction of carbon steel and obey Langmuir adsorption isotherm. Polarisation curves showed their behaviours as mixed-type inhibitors. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability.

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► Novel diquaternary Schiff dibases were synthesized by simple synthetic pathway.
► The Schiff dibases showed good inhibition efficiency for carbon steel in 1 M HCl.
► The efficiency increased by increasing inhibitors concentration and exposure time.
► The mechanism was mixed physical–chemical adsorption and obeys Langmuir isotherm.
► Inhibitors are mixed-type inhibitors influence both cathodic and anodic reactions.