Corrosion inhibitory effects of a new synthetic symmetrical Schiff-base on carbon steel in acid media

In this investigation, the inhibitory effect of a new synthesised tetra-dentate Schiff-base, bis-(2-hydroxy-1-naphthaldehyde) 1,6-hexadiamine (A(1)), on the corrosion of carbon steel in 1 M HCl and 0.5 M H2SO4 media solutions was studied using various techniques including electrochemical impedance spectroscopy polarisation curves and weight loss. The new compound was shown to be a very good inhibitor and had better behaviour in 1 M HCl than was the case in 0.5 M H2SO4. Potentiodynamic polarisation tests showed that this inhibitor had both cathodic and anodic action. Changes in Tafel and impedance parameters (I-corn, R-ct and C-dl) indicated that the absorbed protective film grows with increasing exposure time and concentration of inhibitor. The maximum inhibition efficiency was approximately 97 per cent and 95 per cent at 100 ppm (A(1)) in 1 M HCl and 0.5 M H2SO4. The adsorption of this inhibitor on a carbon steel surface in both acidic media followed Langmuir adsorption isotherm behaviour.