Inhibition of the corrosion of mild steel in acidic media by use of a new antipyridine derivative

The activity of 4-[5-((4-chlorophenyl)diazenyl)-2-hydroxybenzylideneamino)-1,5-dimethyl-2-phenyl-1H-pyrazole-3-(2H)-one (CDHBAP) against corrosion of mild steel in 1 M H2SO4 solutions has been investigated by measurement of weight loss and by potentiodynamic polarization and AC impedance studies. The results obtained indicate that CDHBAP is a good inhibitor; its efficiency reaches 99 % at 100 ppm. Polarization studies show that CDHBAP inhibits corrosion of mild steel by means of a mixed-mode mechanism. AC impedance results confirm adsorption of the CDHBAP at the mild steel-acid interface. A decrease in inhibition efficiency is observed with increasing temperature, and activation energies increase in the presence ofCDHBAP. Physical adsorption is proposed from the trend of inhibition efficiency and the values of Delta G(ads)(0). Formation of a protective layer against acid attack was confirmed by use of FT-IR and UV-visible spectroscopy, X-ray diffraction analysis, and scanning electron microscopy.