Isonicotinohydrazide Chalcone and Its Ni Complex as Corrosion Inhibitors during Acid Cleaning: Theoretical and Experimental Approaches

Abstract

The reaction of isonicotinohydrazide (1) with ¹H-indole-3-carbaldehyde (2) to produce the corresponding (Z)-N'-((1H-indol-3-yl)methylene) isonicotinohydrazide (Ch) was investigated.A novel Ni complex was synthesized from this chalcone (ChN).These compounds were theoretically studied.Amaximum inhibition efficiency of 82.4% and 73.5% for the Ch and ChN inhibitors respectively from weight loss whileit was ~86.9% and ~92.3% for the Ch and ChN inhibitorsrespectively from potentiodynamicpolarization.The polarization resistance for the ChN inhibitor was higher than that for the Ch inhibitor and concomitant decrease in the corrosion rate with increasing the ChN inhibitor concentration was observed. The K<inf>ads</inf> was 11.4824 M^-1and 6.8667 M^-1 for Ch and ChN inhibitors respectively. The free energy of adsorption (ΔG^o<inf>ads.</inf> )was found to be - 12.1685 kJ mol^-1 for the Ch inhibitor and -14.7326 kJ mol^-1 for the ChN inhibitor. This indicates that both the Ch and ChN inhibitors were physically adsorbed onto the surface of the mild steel, with the ChNbeing preferentially adsorbed. Raman spectroscopy analysis of the mild steel reveals the presence of γ-FeOOH on its surface while additional peaks were detected after the addition of the Ch and ChN inhibitors associated with the adsorption of these inhibitors.