Search

The influence of thiophene and five of its substituted derivatives on the corrosion inhibition of steel in 0.5 m H2SO4 solution was studied using weight-loss, electrochemical polarisation, and impedance measurements. 5-tert-butoxythiophene-2-carbaldehyde phenylhydrazone (TBCP) is the best inhibitor and its inhibition efficiency increases with increase in concentration to attain 87% at 5×10−3 m. Potentiodynamic polarisation studies clearly reveal that it acts essentially as a cathodic inhibitor. The partial π-charge on atoms has been calculated. A correlation between the highest occupied molecular orbital E HOMO and inhibition efficiencies was sought. The inhibition efficiency of TBCP is not affected by rise in temperature in the range 298–353 K. E% values obtained from weight-loss and electrochemical methods were in good agreement. Adsorption of TBCP on steel has an S-shaped adsorption isotherm.

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.