Inhibition of Mild Steel Corrosion by Purpald in Highly Sulfuric Acid Solution

The inhibition of mild steel corrosion in 2.5M H2SO4 solution by purpald (4-Amino-3-hydrazino-5-mercapto-1,2,4-triazole, 4-Amino-5-hydrazino-1,2,4-triazole-3-thiol) at 30 degrees C was investigated by means of electrochemical polarization and electrochemical impedance spectroscopy (EIS). Potentiodynamic polarization results were comparable with those obtained by impedance measurements. Results showed that purpald performed excellent as inhibitor for mild steel corrosion in 2.5M H2SO4 solution and it attains an efficiency of more than 95% at 4x10(-4) M at 30 degrees C. The inhibition efficiency increases with an increase in the concentration of purpald. Polarization curves show that purpald is a mix-type inhibitor. Changes in impedance parameters (charge transfer resistance, R-ct, and double layer capacitance, C-dl) were indicative of adsorption of purpald on the mild steel surface, leading to the formation of protective films.