RETRACTED ARTICLE: Investigation on Adsorption and the Corrosion Inhibition Effect of Some Novel Hydrazide Derivatives f
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INTRODUCTION
CORROSION of mild steel especially in acidic media is a matter of concern among scientists, academics, and industrialists and has received a considerable amount of attention.[1] Because they are inexpensive and have wide applicability, the use of inhibitors is widely practiced to protect metals against corrosion, especially in acidic media. These inhibitors usually adsorb on the metal surface, forming protective film by chemisorptions or a physisorption mechanism, and block the active sites there.[2–6] Generally, it is agreed that organic compounds containing multiple bonds, heteroatoms such as nitrogen, oxygen, and sulfur, as well as aromatic rings in their structure often show good corrosion inhibition efficiency for mild steel in acidic media.[7–9] Literature survey reveals that due to environmental concerns, much attention is being paid to the development of nontoxic corrosion inhibitors. Nicotinic hydrazones are one of the important classes of nontoxic imines, which have various pharmacological properties such as being anti-inflammatory, an analgesic agent, and antimicrobial.[10] Recently, we have reported
DHARMENDRA KUMAR SINGH is with the Department of Chemistry, P.K. Roy Memorial College, Dhanbad 826004, India. Contact email: [email protected], [email protected] DEBASIS BEHERA is with the Department of Chemistry, Manipal University, Jaipur-303007, India. MANTU KUMAR SINGH, G. UDAYABHANU, and ROHITH P. JOHN are with the Department of Applied Chemistry, Indian School of Mines, Dhanbad 826004, India. Manuscript submitted October 20, 2016.
METALLURGICAL AND MATERIALS TRANSACTIONS A
the inhibitive effect of 4(N,N-dimethylamino)benzaldehyde nicotinic hydrazone on corrosion of mild steel in 1 M HCl.[11] It has shown good corrosion inhibition efficiency in the concentration range of 0.25 to 6.00 mM, which incited us to investigate another important nicotinic hydrazone as a corrosion inhibitor for mild steel in acidic media. The inhibition efficiency is related to the chemical composition, molecular structure, and molecular parameters of the inhibitors.[12] Quantum chemical calculations have proved to be an important tool to determine important molecular parameters and to correlate them with the inhibition ability of the inhibitors.[13–15] The objective of this article is to investigate some nicotinic hydrazones, namely, N¢-(thiophene-2-ylmethylene)nicotinic hydrazone (TNH) and N¢-(pyrrol-2-ylmethylene)nicotinic hydrazone (PNH), as novel corrosion inhibitors for mild steel in 1 M HCl solution using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), a field emission–scanning electron microscope (FE-SEM), and an atomic force microscope (AFM). Furthermore, quantum chemical calculations have been performed by the density functional theory (DFT) to understand the mechanism of adsorption along with the relationship between molecular parameters and inhibitive performance.
II.
EXPERIMENTAL
A. Synthesis of Nicotinic Hydrazones Pyrrole-2-aldehyde or Thiophene-2-aldehyde was slowly
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