Abstract
The deterioration of iron-based alloys, especially mild steel (MS) is one amongst the most challenging problems faced in various chemical industries. The present work focuses on the potential activity of a naphthalimide derivative namely 2-(2-hydroxyethyl)benzo[de]isoquinoline-1,3-dione (HBIQ) as corrosion inhibitor for MS in sulfamic acid (SA) medium in the temperature range from 303 to 323 K. Potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) were employed in the experimental measurement and HBIQ exhibited 89% inhibition at its optimum concentration. HBIQ demonstrated electrostatic interactions with MS surface and behaved as a mixed type of inhibitor by obeying Langmuir’s isotherm model. Surface characterization of uninhibited and inhibited MS specimens combined with elemental analysis data provided clear evidences for the formation of a protective adsorption layer of HBIQ on MS surface. Spectral analysis such as Ultraviolet visible and Fourier Transform Infra-red spectral analyses were carried out in order to confirm the adsorption of HBIQ on to the metal surface. The density functional theory calculations supported the experimental results and indicated the contribution of delocalized π-electrons in the naphthalimide unit and the lone-pair electrons of oxygen in the carbonyl and hydroxyl group for improved adsorption of HBIQ onto MS surface, thereby reducing the corrosion of the alloy in SA environment.Graphic abstract
Highlights
Among the iron-based alloys, mild steel (MS) has drawn significant attention due to its higher mechanical strength, ductility, machinability and weldability compared to other alloys, and easy availability and exceptionally low cost (Ahmed et al 2019)
Shimadzu IR spirit spectrophotometer was used to record the FTIR spectrum of HBIQ molecule and the scraped out product of the adsorbed protective layer formed on the MS surface exposed to 7.5 × 1 0–4 M HBIQ in 1 M sulfamic acid (SA) acid solution
A naphthalimide derivative HBIQ was prepared by easy synthetic protocol from acenaphthene and following inferences are drawn from the various investigations performed to study its corrosion inhibition capability
Summary
Among the iron-based alloys, mild steel (MS) has drawn significant attention due to its higher mechanical strength, ductility, machinability and weldability compared to other alloys, and easy availability and exceptionally low cost (Ahmed et al 2019). The SA features many attractive properties including non-volatile, non-hygroscopic, odorless, stable and ability to act as strong acid in aqueous solution with significantly less corrosion to the metals exposed These unique characteristics allow its usage in many chemical industries for dissolving hard iron oxide and variety of water-formed scales and deposits from the metal surface without any causing any chloride-induced stress corrosion cracking (SCC) (Fouda et al 2014). It is widely used as a cleaning agent in a variety of industrial applications including cooling tower systems, desalination plants, heat exchangers and flash evaporators. The absorption spectrum of the same solution was further recorded after immersing MS specimen for 3 h
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