Newly synthesized N-(5-nitro-2-hydroxybenzylidene)pyridine-4-amine as a high-potential inhibitor for pipeline steel corrosion in hydrochloric acid medium
Nkem B. Iroha, Cordelia U. Dueke‐Eze, Abosede James, T.M. Fasina
Abstract
N-(5-nitro-2-hydroxybenzylidene)pyridine-4-amine (NHPA) synthesized by the condensation of 4-aminipyridine with 5-nitro-2-hydroxybenzaldehyde was tested as an inhibitor for API J55 carbon steel (CS) corrosion in 1 M HCl utilizing electrochemical and gravimetric measurements. Inhibition was enhanced with increase in NHPA concentration and at optimum concentration of NHPA (2.0 g L−1) and 30 °C, 96.28% inhibition efficiency was obtained with gravimetric method, 93.03% with electrochemical impedance spectroscopy (EIS) technique and 92.09% with potentiodynamic polarization technique. Polarization studies reveal that NHPA is mixed type inhibitor but predominantly anodic. EIS measurement revealed increased charge-transfer resistance (Rct) and diminished double-layer capacitance (Cdl) upon addition of NHPA, which brought about improved inhibition. The inhibition is known to be by adsorption on the J55 CS surface which follows Langmuir isotherm. Surface analysis performed using scanning electron microscopy with energy dispersive X-ray (SEM-EDX) analysis showed improved surface morphology of J55 CS in presence of NHPA.