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Inhibition by some newly synthesised pyridazine compounds of corrosion of pure iron in 1 M HCl solution has been studied using weight loss measurements, polarisation and impedance spectroscopy methods. The inhibiting action is more pronounced with stet-5-benzyl-6-methylpyridazin-3-yl thioethanoic (P1) and (5-benzyl-6-methylpyridazin-3-yl) ethyl thioethanoate (P3) and their inhibition efficiency increases with concentration to attain the maximum value of 85% and 81% at the 10−4 M, respectively. We note good agreement between gravimetric and electrochemical methods (potentiodynamic polarisation and impedance spectroscopy (EIS)). Polarisation measurements show also that the pyridazines act essentially as cathodic inhibitors. The cathodic curves indicate that the reduction of proton at the pure iron surface happens with an activating mechanism. The presence of the sulphur atom increases the inhibition efficiency changing the adsorption mechanism.

The inhibition of pure iron in 1 M HCl by new synthesised pyridazine compounds has been studied by weight loss, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements. The results obtained reveal that these compounds are efficient inhibitors. The inhibition efficiency increases with the increase of inhibitor concentration and reached 98% at 10 −4 M for 5-benzyl-6-methyl pyridazine-3-thione. Potentiodynamic polarisation studies clearly reveal that the presence of pyridazines does not change the mechanism of hydrogen evolution and that they act essentially as cathodic inhibitors. The temperature effect on the corrosion behaviour of pure iron in 1 M HCl without and with the pyridazines at 10 −4 M was studied in the temperature range from 298 to 353 K. EIS measurements show that the increase of the transfer resistance with the inhibitor concentration.