Study of Synergistic Effect of Iodide on the Corrosion Antagonistic Behaviour of a Heterocyclic Phenylhydrazone in Sulphuric Acid Medium on Carbon Steel

Abstract

Synergistic effect of KI on the corrosion inhibition efficiency of 3-acetylpyridine phenylhydrazone (3APPH) on carbon steel (CS) in 0.5 M sulphuric acid solution has been investigated using gravimetric studies, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization studies. Gravimetric corrosion studies revealed that 3APPH showed moderate corrosion inhibition efficiency up to 8 h and beyond this period it showed corrosion accelerating behavior. This antagonistic effect of 3APPH is due to the hydrolysis of the molecule in acidic medium. A very high percentage of inhibition efficiency at 24 h was obtained on the addition of KI due to the synergistic effect of iodide ions. The adsorption of 3APPH and 3APPH + KI on the surfaces of the corroding metal obey Langmuir isotherm as obtained by impedance measurements. Polarization studies revealed that 3APPH act as a mixed type inhibitor. Thermodynamic parameters (ads , Δ 0 ads) were derived from the adsorption isotherms. Surface morphology of the corroding metal was investigated by SEM analysis.

Chemical modification at the surface and corrosion inhibition response of two semicarbazones on carbon steel in HCl medium

“…Intense hydrolysis to this molecule occurred in sulphuric acid, which was confirmed by UV-visible spectroscopy. The same compound showed very high inhibition efficiency ([99 % at 1.0 mM as per electrochemical studies) on CS surface in 0.5 M H 2 SO 4 in the presence of trace amount of KI [11]. It is quite sure that the corrosion inhibiting capacity of a molecule is a combined effect of its molecular structure, geometry and the way in which it behaves in the aggressive medium in the presence of a metal.…”

“…Molecules equipped with active corrosion inhibition sites such as hetero atoms like O, S, N, aromatic rings and Schiff bases are found to act as efficient corrosion inhibitors in aggressive media [1][2][3][4][5][6][7]. A few semicarbazones and hydrazones exhibited good corrosion protection ability due to the presence of C=N group [11,16]. Electronic effects such as inductive, mesomeric, etc., affect the corrosion inhibition power of molecules.…”