Inhibiting effects of 5-substituted isatin-based Mannich bases on the corrosion of mild steel in hydrochloric acid solution

Newly Synthesized Morpholinyl Mannich Bases as Corrosion Inhibitors for N80 Steel in Acid Environment

New Mannich bases, 3-morpholino-1-phenylpropan-1-one (MPO) and 3-morpholino-1-phenyl-3-(pyridin-4-yl) propan-1-one (MPPO), were synthesized, characterized, and studied as corrosion inhibitors for N80 steel in 1 M hydrochloric acid (HCl) solution using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and FT-IR spectroscopy. The inhibition efficiency increases with increasing inhibitor concentrations, and the corrosion inhibition efficiency of the MPO and MPPO could reach 90.3% and 91.4%, respectively, at a concentration of 300 ppm at 305 K. The effect of the temperature on the corrosion inhibition behavior of inhibitors was discussed. Electrochemical tests showed that the synthesized inhibitors are mixed. The EIS test results showed that the presence of MPO and MPPO reduced the double-layer capacitance in the corrosion process, thereby reducing the charge transfer resistance. The SEM and EDX results showed that the MPO and MPPO formed a uniform adsorption film on the surface of the N80 steel. The adsorption mechanism of the inhibitors was simulated with different adsorption models and the results showed that the inhibitors were the chemisorbed type. The results of the FT-IR spectroscopy proved that the inhibitor interacted with metal atoms on the steel surface.

Mannich Base as an Efficient Corrosion Inhibitor of AA6061 in 0.5 M HCl: Electrochemical, Surface Morphological and Theoretical Investigations

The inhibition action of a Mannich base, N-(1- morpholinobenzyl) semicarbazide (MBS), was examined on AA6061 corrosion in 0.5 M HCl solution at varied temperatures (303 to 323 K). The testing was performed by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. The inhibition performance of MBS was improved with an increment in its concentration (0.01–2.56 mM) and temperature rise (303 to 323 K). MBS showed a mixed inhibitor behavior at all concentrations and temperatures range studied. MBS displayed the highest inhibition efficiency of 98% at 2.56 mM and 323 K. Inhibitor followed mixed adsorption on the alloy surface and obeyed the Langmuir isotherm model. The results obtained from the EIS were in good agreement with that of the PDP results. An appropriate mechanism was proposed for the corrosion inhibition of AA6061. Inhibitor molecules adsorption on alloy surface was confirmed by surface morphology testing by a scanning electron microscope (SEM) and atomic force microscope (AFM). Theoretical studies using density-functional theory (DFT) confirmed the experimental results.

Synthesis and inhibitive characteristic of two acryloyl chloride derivatives towards the corrosion of API 5L X52 carbon steel in hydrochloric acid medium

Two new organic based corrosion compounds were prepared from Acryloyl chloride are namely: N,N-bis(2-hydroxyethyl) acrylamide (DEA) and N-(2-hydroxyethyl) acrylamide (MEA). The prepared compounds were studied as corrosion inhibitors for carbon steel (CS) in 1 M hydrochloric acid solution while the efficiency of the prepared compounds were studied through different chemical (weight loss, WL) and electrochemical techniques [potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS)] in addition to, the theoretical techniques as Quantum chemical calculations, Monte Carlo simulation and the surface morphology study using atomic force microscopy (AFM). The obtained results showed that the investigated compounds are working as good corrosion inhibitors, the inhibition efficacy (%IE) increases with the increase of the compound concentrations. However, the %IE decreases with the rise in the temperature proving that the adsorption of the inhibitor molecules on the CS surface is physisorption, while the polarization data revealed that these compounds are classified as mixed kind inhibitors, that inhibits both anodic and cathodic reactions. Results reveal that DEA and MEA exhibit an excellent %IE of 89.2 and 71.6% at 60 ppm for DEA and MEA, respectively. The adsorption of the inhibitor molecules on CS surface following Langmuir adsorption isotherm. There is a strong matching between results obtained from experimental and theoretical studies. The order of the investigated inhibitors based on the %IE is DEA > MEA.

Comparative Investigation of Corrosion-Mitigating Behavior of Thiadiazole-Derived Bis-Schiff Bases for Mild Steel in Acid Medium: Experimental, Theoretical, and Surface Study

In the present study, comparative analyses of corrosion inhibition property of few thiadiazole-derived bis-Schiff bases for mild steel in 1 M HCl were done. Various electrochemical experiments (electrochemical impedance spectroscopy and potentiodynamic polarization), as well as weight loss experiments, were employed to study the anticorrosion activity of bis-Schiff bases as inhibitors. The highest inhibition efficiency was obtained at an optimum concentration of 125 ppm for all inhibitors. Potentiodynamic polarization studies explain the mixed type but predominantly the cathodic nature of all inhibitors. The Langmuir adsorption isotherm was used to describe the mechanism of adsorption. The change in the value of activation energy on the addition of inhibitors reflects the mixed mode of interaction between the inhibitor and metallic surface. Scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analyses confirmed the adsorption of bis-Schiff bases on the metal surface and thereby shielding from corrosion. Besides, the relevance between inhibition efficiency and the molecular structure of an inhibitor was theoretically examined via quantum chemical calculations and molecular dynamics simulations. All the results show consistent agreement with each other.

Monitoring the Interaction of Two Heterocyclic Compounds on Carbon Steel by Electrochemical Polarization, Noise, and Quantum Chemical Studies

A heterocyclic phenylhydrazone 2-[(E)-(2-phenylhydrazinylidene)methyl]pyridine (P2APH) and its reduced form 2-[(2-phenylhydrazinyl)methyl]pyridine (RP2APH) were synthesized, characterized, and subjected to corrosion inhibition investigation on carbon steel (CS) in 1 M HCl using gravimetric, polarization, electrochemical noise, quantum chemical, and surface studies. P2APH showed more inhibition capacity than RP2PPH. But RP2PPH was very stable in acid medium and showed pronounced corrosion inhibition efficacy for days. Energy of HOMO and LUMO, their difference, number of electrons transferred, electronegativity, chemical hardness, and so forth were evaluated by quantum chemical studies. Agreeable correlation was observed between the results of quantum chemical calculations and other corrosion monitoring techniques.

Some Thiophene Derivatives as Corrosion Inhibitors for Carbon Steel in Hydrochloric Acid

Corrosion inhibitive performance of some thiophene derivatives during the acidic corrosion of carbon steel surface in 1 M HCl was investigated by chemical technique (weight loss) and electrochemical techniques (potentiodynamic polarization, electrochemical frequency modulation, and electrochemical impedance spectroscopy). The effect of temperature on the corrosion rate was investigated by the weight loss method, and some thermodynamic parameters for corrosion and adsorption processes were determined and discussed. The results show that the inhibition efficiency increased with the increase in inhibitor concentration and temperature. The adsorption of thiophene derivatives on the carbon steel surface obeys Langmuir adsorption isotherm. The obtained results indicated that the investigated compounds are chemically adsorbed on the steel surface. Potentiodynamic polarization studies showed that these compounds are mixed-type inhibitors and the results obtained from the techniques are in good agreement.