Novel thiophene symmetrical Schiff base compounds as corrosion inhibitor for mild steel in acidic media

doi:10.1016/j.corsci.2011.01.022

Corrosion Science

Volume 53, Issue 4, April 2011, Pages 1484-1488

https://doi.org/10.1016/j.corsci.2011.01.022 Get rights and content

Abstract

The inhibiting effect of two Schiff bases on the corrosion of the mild steel (MS) in 1 M HCl has been studied by electrochemical impedance spectroscopy (EIS) and Tafel polarisation measurements. The Schiff bases, 4,4′-bis(3-carboxaldehyde thiophene) diphenyl diimino ether (L₁) and 4,4′-bis(3-carboxaldehyde thiophene) diphenyl diimino ethane (L₂), were synthesized using 3-carboxaldehydethiophene and its corresponding amine. Polarisation curves reveal that both compounds are mixed type (cathodic/anodic) inhibitors and inhibition efficiency (% IE) increases with increasing concentration of compounds. It is suggested that their effects depend on their concentrations and the molecular structures. Adsorption of compounds on mild steel surface is spontaneous and obeys Langmuir’s isotherm.

Research highlights

► The aim of the present investigation is to examine the inhibitory action of two Schiff bases. ► Compounds are mixed type (cathodic/anodic) inhibitors. ► Inhibition efficiency (% IE) increases with increasing concentration of compounds. ► Adsorption of compounds on mild steel surface obeys Langmuir’s isotherm.

Introduction

The use of inhibitors is one of the most practical methods for protection against corrosion especially in acidic media [1], [2]. Acid solutions are generally used in several industrial processes. HCl is widely used in picking solutions. Because of their aggressiveness, the use of corrosion inhibitors is considered as the most effective method for the protection of many metals and alloys against such acid attack [3], [4], reduces the dissolution rate of metals. Compounds containing functional groups with heteroatoms, which can donate one pair of electrons, are found to be very efficient as inhibitors against metal corrosion in many environments. Many heterocyclic compounds with polar groups and/or π electrons are efficient corrosion inhibitors in acidic solutions. Organic molecules of this type can adsorb on the metal surface and form a bond between their N-electron pair and/or π electron cloud and the metal surface, thereby reducing the corrosion in acidic solutions [5], [6], [7]. Some Schiff bases inhibitors have been previously reported as effective corrosion inhibitors for various metals in acid media, such as Schiff bases containing thiophene substituents [8], [9] and furoin thiosemicarbazone [10].

The aim of the present investigation is to examine the inhibitory action of two Schiff bases containing nitrogen and sulphur het-eroaromatic compound as substituents in their structures for the corrosion of mild steel in 1 M HCl solution. Effects of concentrations and molecular structures on the inhibition efficiencies of the selected Schiff bases have been studied systematically. Differences in behaviour of inhibitors were explained based on structural properties of investigated inhibitors.

Section snippets

Experimental

Compounds L₁ and L₂ were synthesized according to published methods [11], [12]. Diamine (1 mM) (hot ethanol, 20 mL) was added dropwise 2 mM of thiophene 3-carbaldehyde (Fluka Chemical Company). These products are soluble in ethanol/H₂O and DMF solutions. The structures of these products were confirmed by elemental analysis (service d’Analyse, ICSN- CNRS, Gif sur Yvette (France)) and FT-IR spectroscopy. The molecular structures of L₁ and L₂ are shown in Fig. 1. Elemental analyses: Anal. Cal. For L₁

Tafel polarisation measurements

Fig. 2, Fig. 3 show anodic and cathodic polarisation plots recorded on mild steel electrode in 1 M HCl in absence and presence of different concentrations of L₁ and L₂ inhibitors. Table 1 shows the electrochemical corrosion kinetic parameters, i.e., corrosion potential (E_corr), cathodic and anodic Tafel slopes (b_c, b_a) and corrosion current density i_corr obtained by extrapolation of the Tafel lines. As it was expected both anodic and cathodic reactions of mild steel electrode corrosion were

Conclusion

The corrosion behaviour of mild steel was investigated in 1 M HCl with and without addition of various concentrations of Schiff bases at different concentrations, using potentiodynamic and electrochemical impedance techniques. Polarisation curves reveal that both compounds are mixed type (cathodic/anodic) inhibitors and inhibition efficiency (% IE) increases with increasing concentration of compounds. The adsorption of Schiff bases on mild steel in 1 M HCl solution obeys Langmuir adsorption

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Mild steel corrosion inhibition comparison between indole-5-carboxylic acid and benzofuran-5-carboxylic acid: An integrated experimental and theoretical study
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Corrosion inhibition capabilities of Indole-5-carboxylic acid (IC) and Benzofuran-5-carboxylic acid (BC) on mild steel have been comprehensively investigated using various techniques, including Potentiodynamic Polarization Measurement (PPM), electrochemical impedance spectroscopy (EIS), and scanning electrochemical microscopy (SEM). The results from polarization tests demonstrated that both IC and BC effectively reduced the corrosion current densities of both cathodic and anodic reactions occurring on the metal surface. Through EIS analysis, it was observed that the inhibitory efficacy of IC and BC increased with higher inhibitor concentrations. At a temperature of 30°C, the solution containing 10⁻²M IC and 10⁻²M BC exhibited the maximum inhibitory efficiency, with IC achieving 92.19% and BC achieving 75.00%. The adsorption behavior of the inhibitors was found to follow the Langmuir isotherm, suggesting a monolayer adsorption process. Additionally, quantum chemical calculations were carried out to assess the molecular parameters of the inhibitors thoroughly. These calculations consistently indicated that IC exhibited superior inhibitory properties compared to BC. Furthermore, molecular dynamics simulations were employed to gain insights into the optimal adsorption configuration of the inhibitors on the Fe(110) surface. The results revealed that IC possessed a higher binding energy with the Fe(110) surface, confirming its superior ability to inhibit steel corrosion compared to BC.
Efficient inhibition of mild steel corrosion in acidic medium by novel pyrimidine derivatives: Inhibitive effect evaluation and interface adsorption mechanism
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Corrosion of steel occurs due to the rough working environment in which it is used. It accelerates the deterioration of the steel components and results in substantial financial loss. Continuous research has been carried out to prevent or reduce the corrosion of steel and other metals because these materials have so many industrial applications.
The inhibition performance of three new organic substances, N1-(3-morpholinopropyl)-N1-((pyridine-2-yl)methyl)propane-1,3-diamine (I1), 2‑methoxy-6-(((3-((3-morpholinopropyl)(pyridin-2-ylmethyl)amino)propyl)imino)methyl)phenol (I2), and its reduced form, 2‑methoxy-6-(((3-((3-morpholinopropyl)(pyridin-2-ylmethyl)amino)propyl)imino) methyl) phenol (I3), on corrosion of the P460N in 3.5 wt.% NaCl solution was investigated by potentiodynamic polarization (PDP), EIS, immersion tests, and SEM techniques.
A novel material exhibiting superior corrosion protection capabilities for steel was synthesized, and its efficacy was validated through both electrochemical and non-electrochemical testing methods. Comparing the OCP values in the blank and inhibitor-containing solutions shows a negative shift. According to PDP experiments, the highest value of i_corr occurs with the P460N electrode in the inhibitor-free solution (79.4 μA.cm⁻²). Meanwhile, in the case of the highest concentration of I1, I2, and I3 inhibitors, a significant reduction in the corrosion rate was observed, with reductions of 6, 17, and 22 times, respectively. Notably, the reduced form (I3) exhibited exceptional protection against corrosion. PDP results confirmed that the inhibition efficiency reached the highest value of 84.1, 94.3, and 95.5% for I1, I2, and I3 at 2.0 mM concentration. From the EIS measurements, the inhibition performance of inhibitors follows the order I3 > I2 > I1 at equal concentration. Based on the immersion test results and SEM-EDS evaluation, the reduced sample (I3) demonstrated significantly lower corrosion over an extended period, indicating excellent long-term stability in the 3.5% NaCl solution. The electrochemical (PDP and EIS), and non-electrochemical (immersion tests) data confirmed that the inhibition efficiency of the inhibitor of I3 was better than the two other compounds. SEM and EDS analysis showed severe corrosion for the P460N surface without an inhibitor, and corrosion products such as iron oxide and trapped NaCl in porosity appeared very uneven, with different shapes. The study explored four absorption mechanisms: Langmuir, Temkin, Freundlich, and Frumkin. The three new inhibitors were found to adhere to the Langmuir adsorption isotherm with a high correlation coefficient of approximately 0.999. Moreover, these inhibitors demonstrated mixed inhibition behavior for P460N steel in a 3.5% NaCl solution.
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Aiming to provide a wide perspective on metal-corrosion inhibition modeling the classical, modern and the so-called functional surface dependency adsorption isotherms were reviewed in order to clarify the working frameworks from either physical or chemical bonding continuous that best apply on various electro-chemical circumstances. This way, from the fashioned Langmuir isotherm, to its multi-scalar versions: the Freundlich isotherm to Temkin isotherm suitable for heterogeneous metal surfaces have been discussed. As such, the Flory - Huggins and Bockris - Swinkels isotherms allow the evaluation of the number of adsorbed water molecules replaced by one inhibitor molecule. The El-Awady isotherm is highlighting the number of layers of inhibitor molecules from the metal-solution interface. The Volmer isotherm is accounting for the possibility of adsorbate molecules to move from one adsorption site to another, in the absence of any lateral effects. The Dubinin-Radushkevich isotherm recently used in corrosion studies models the corrosion inhibitors via the adsorption energy E_ads. All of presently considered isotherms may contribute in better characterizing nano-materials and surface processes via molecular electrochemistry and metal-ionic interaction on a hierarchical inclusive analytical framework.

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Published by Elsevier Ltd.

Novel thiophene symmetrical Schiff base compounds as corrosion inhibitor for mild steel in acidic media

Abstract

Research highlights

Introduction

Section snippets

Experimental

Tafel polarisation measurements

Conclusion

J. Electroanal. Chem.

Mater. Chem. Phys.

Electrochim. Acta

Mater. Chem. Phys.

Corros. Sci.

Corros. Sci

Mater. Chem. Phys.

Corros. Sci.

Polyhedron

Electrochim. Acta

Appl. Surf. Sci.

Corros. Sci.

Corros. Sci.

Corros. Sci.

Mater. Chem. Phys.