Inhibitory efficiency of oxalic N-phenylhydrazide-N′-phenylthiosemicarbazide on corrosion of carbon steel in 0·5M H2SO4.

The inhibitory effect of an oxalic type organic compound oxalic N-phenylhydrazide-N′-phenylthiosemicarbazide on the corrosion of carbon steel in 0·5M H₂SO₄ aqueous solution was investigated by different experimental methods; gravimetry, voltammetry and electrochemical impedance spectroscopy. The surface state of the electrode after immersion of the steel coupons in corrosion test solutions, in absence and in presence of the inhibitor was characterised by scanning electron microscopy. The potentiodynamic polarisation measurements showed that the presence of the inhibitor in 0·5M H₂SO₄ decreased both cathodic and anodic processes. The action of this inhibitor is therefore of a mixed type. The electrochemical impedance measurements showed the adsorption of the inhibitor. The inhibitory efficiency reaches a value of 95% at an inhibitor concentration of 10⁻³M. [ABSTRACT FROM AUTHOR]