4-aminoantipyrine as an inhibitor of mild steel corrosion in HCl solution

4-aminoantipyrine (AAP) was tested as a corrosion inhibitor for mild steel in 2 M HCl solution using different techniques: weight loss, potentiodynami c polarization and electrochemical impedance spectroscopy (EIS). The result s showed that AAP is an inhibitor for mild steel in this medium. The inhibi tion was assumed to occur via adsorption of the inhibitor molecule on the m etal surface. In the 20 to 60 degrees C temperature range, the AAP adsorpti on follows the Flory-Huggins isotherm and/or the El-Awady et al. kinetic-th ermodynamic model. The protection efficiency increases with increasing inhi bitor concentration (in the range 10(-3)-10(-2) M) but decreases with incre asing temperature. The thermodynamic functions of dissolution and adsorptio n processes were calculated.