Corrosion behavior of mild steel in hydrochloric acid solution in presence of nicotinic acid derivatives

The inhibition effect of the synthesized organic inhibitor namely nicotinic acid hydrazide (NAH) and its benzylidine derivative (NABH) on the corrosion of mild steel in1M hydrochloric acid has been investigated using weight loss, Electrochemical Impedance Spectroscopy (EIS) and Tafel polarization measurements. The inhibition efficiencies obtained from all methods employed are in good agreement with each other. The obtained results show that the compounds NAH and NABH are very good inhibitors with efficiency 90% and 94% respectively at 1.0 mM additive concentration in acid solution. The inhibition efficiency increases with increase of inhibitor concentration. Changes in impedance parameters (Rt and Cdl) were indicative of adsorption of the compound on the metal surface, leading to the formation of a protective film. Tafel polarization measurements showed that the inhibitors are mixed type. Adsorption of the inhibitor on the surface of the mild steel in 1M hydrochloric acid was found to obey Langmuir’s adsorption isotherm. The activation energy and free energy of adsorption process were calculated and discussed.