Corrosion inhibition effects of concentration of 2-oxo-3- hydrazonoindoline in acidic solution, exposure period, and temperature

The topic which has garnered a lot of attention is corrosion prevention, since it is among the most productive and economical means of protecting metallic substrates. Active organic inhibitors with heterocyclic and aromatic rings have been the subject of a number of published articles and letters. Using weight loss (WL) techniques, the 2-oxo-3-hydrazonoindoline (OHI) isatin Schiff base's capacity to prevent mild steel (MS) corrosion in 1.0 M hydrochloric acid was investigated. Studies were conducted for the concentration, immersion period, and environmental temperature conditions that affect corrosion inhibition ability. OHI has the maximum inhibitory efficiency at a concentration of 0.5 mM at 303 K, which is 91.8%. OHI really has excellent acidic corrosion inhibition properties because of the heteroatoms (nitrogen and oxygen), benzene, and heterocyclic rings that are present. WL tests demonstrated that the inhibitory efficacy increases with longer immersion times. Moreover, at the highest tested temperature of 333 K, the inhibitory efficacy slightly reduces. In the adsorption process on a metallic substrate, the OHI molecules obey the Langmuir adsorption isotherm model. The free energy value indicated that the inhibition process of OHI molecules on the metallic substrate was following both chemisorption and physisorption mechanisms. The mechanism of inhibition can be explained by two important elements: the application of density functional theory via quantum chemical calculations, and the chemical structure of the inhibitor under investigation. It was found through this study that there is a close agreement between the experimental and the theoretical results.