Corrosion Inhibition of Carbon Steel by 1-Phenyl-3-Amino-5-Pyrazolone in H2SO4 Solution

Corrosion inhibition efficiency of 1-phenyl-3-amino-5-pyrazolone (PAP) on mild steel in 0.5 mol/L sulfuric acid (H2SO4) solution was investigated by weight loss measurements, potentiodynamic polarization technique, electrochemical impedance spectroscopy (EIS). Measurement of the weight loss shows an inhibition efficiency of about 58.9% in the presence of 0.05 mmol/L PAP, which increases to about 93% at a PAP concentration of 1 mmol/L. Potentiodynamic polarization measurements and EIS reveal that PAP is an excellent corrosion inhibitor of mild steel in 0.5 mol/L H2SO4 solution with an efficiency higher than 98% at 1 mmol/L at 298 K. The inhibitor adsorption on the steel surface follows the Langmuir adsorption isotherm.