Phenylhydrazone Derivatives as Corrosion Inhibitors for -α- Brass in Hydrochloric Acid Solutions

The inhibition effect of some phenylhydrazone derivatives, namely,.[ ethyl(2Z)-cyano[(4E)-5-oxo-3-phenyl-4-(phenylhydrazono)-1,3- thia-zolidin-2-ylidene] acetate (A), ethyl(2Z)-cyano[(4E)-5-oxo-3phenyl-4-(p-methylphenylhydrazono)- 1,3-thiazolidin-2-ylidene] acetate (B), ethyl(2Z)-cyano[(4E)-5oxo-3-phenyl-4-(o-methoxyphen-ylhydrazono)- 1,3-thiaz-oli-din-2-ylid-ene] acetate (C) and ethyl(2Z)-cyano[(4E)-5-oxo-3-thiazo-lid-in-2-ylidene] acetate (D) on the corrosion of 70Cu-30Zn brass in 2M HCl solution has been investigated using weight loss and galvanostatic polarization techniques. The percentage inhibition efficiency was found to increase with increasing concentration of inhibitor and with decreasing temperature. The addition of KI to phenylhydrazone derivatives enhanced the inhibition efficiency due to synergistic effect. The adsorption of these inhibitors on the brass surface obeys Temkin isotherm. Some activated thermodynamic parameters were calculated. The addition of these compounds to the potentiodynamic anodic polarization curves of square- brass electrode in chloride solutions shift the pitting potential to more positive values, indicating an increased resistance to pitting attack .