Y. M. Abdallah*a,
Ola. A. El-Gammalb,
Hany M. Abd El-Lateefcd and
K. Shalabi
*b
aDepartment of Dental Biomaterials, Faculty of Oral and Dental Medicine, Delta University for Science and Technology, Gamasa, Egypt. E-mail: dr.ymostafa8@gmail.com; Yasser.Mostafa@deltauniv.edu.eg
bChemistry Department, Faculty of Science, Mansoura University, P.O. Box 70, Mansoura, Egypt. E-mail: dr-kamal@mans.edu.eg
cDepartment of Chemistry, College of Science, King Faisal University, Al-Ahsa 31982, Saudi Arabia. E-mail: hmahmed@kfu.edu.sa
dDepartment of Chemistry, Faculty of Science, Sohag University, Sohag 82524, Egypt
First published on 16th May 2022
Two novel ethanoanthracene-11,12-dicarbohydrazide derivatives N′11,N′12-bis((Z)-4-hydroxybenzylidene)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarbohydrazide (H2HEH) and N′11,N′12-bis((Z)-4-methoxybenzylidene)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarbohydrazide (H2MEH) were synthesized and characterized by FT-IR spectroscopy, electronic spectra, and NMR spectroscopy. These two derivatives as novel anticorrosion inhibitors for N80 steel in a 3.5% NaCl solution were studied using electrochemical techniques including potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM). Corrosion parameters and adsorption isotherms were determined from current–potential diagrams (i.e., Tafel slopes). The impact of temperature and inhibitor concentration on the corrosion performance was studied using the PP method. The PP results suggested mixed-type inhibitors. The inhibition prohibition increased and decreased when the dose was increased and the temperature was increased, respectively. The adsorption of the hydrazides on the N80 exterior followed the Langmuir isotherm. The maximum inhibition proficiency for H2MEH and H2HEH were 93.3% and 92.2%, respectively, at 1 × 10−4 M. Moreover, the investigated surface was studied with the synthesized compounds through X-ray photoelectron spectroscopy (XPS) to confirm the construction of an adsorbed shielding barrier. An evident association was established between the corrosion inhibition proficiency and theoretical variables acquired using the density functional theory (DFT) method and Monte Carlo (MC) simulations. The experimental data were in good agreement with the theoretical results.
Moreover, various studies have recommended the use of heteroatom-containing organic components with functional groups such as –OH, –NH2, –OCH3, –COOH, –SO3H and benzene rings. These compounds have been found to be potential inhibitors since they can react with a metal or alloy to produce a protective film coating on a tested surface.4–7
Quantum chemical computations have been extensively exploited to survey the mechanisms of corrosion and to explain the experimental data.6 They have been used to elucidate vague chemical results and are found suitable for the understanding of corrosion mechanisms in examined particles on a metal exterior.7 The variables in the preparation and electronics of inhibitor components could be explained by the concepts of theoretical estimation using the computerized approaches of quantum chemistry.8
An appropriate approach to corrosion protection on metals and composites is the addition of organic derivatives to corrosive media.9,10
Furthermore, organic inhibitors that include electron-donating heteroatoms such as –N, –O, –S and π-electrons associated with heterocyclic bonds are strong metals and composite inhibitors in corrosive solutions.11–17 An issue with the utilization of corrosion inhibitors is the adsorption of an inhibitor on the external surfaces of metals and composites from a solution. Consequently, the examinations of organic compounds on corroded carbon steel in acidic corrosive media showed many indentations; thus, they are mostly insufficient.18–20
Carbon steel has been examined using different corrosive media, including: hydrazones,21 anti-tuberculosis drugs,22 Stachys byzantina extracts,23 interfacial assembled mesoporous polydopamine nanoparticles,24 Zn(II)-metal–organic networks using lemon verbena leaf extract,25 2-aminopyridine derivatives,26 and benzodiazepine derivatives.27
The environmental significance of hydrazide derivatives is due to their biocompatibility. Hydrazides have been explored for their corrosion mitigating properties.28 In this study, the effectiveness of hydrazide derivatives as corrosion inhibitors were on the basis of the fact that they have a wide spectrum of medicinal chemistry use due to their biological features such as analgesic and anti-inflammatory effects, which have been well documented in numerous studies.29,30 Isonicotinic acid hydrazide is unquestionably effective in tuberculosis treatment, whereas fatty acid hydrazides have been applied as fabric processing agents.31
In acidic and neutral environments, hydrazide derivatives have been approved as corrosion inhibitors. The corrosion inhibitors, including salicylic acid, anthranilic acid, and benzoic acid hydrazides with AOH, ANH2, and AH as characteristic substituents, have been investigated. The potentiodynamic polarization (PP) technique revealed that they showed a mixed-type inhibitory activity for mild steel corrosion.32 Kumari et al.33 investigated the aromatic hydrazide derivative of 2-(3,4,5-trimethoxybenzylidene) hydrazinecarbothioamide as a mixed-type inhibitor with prohibition efficacy that increased in both cathodic and anodic directions. Ferrocene carboxaldehyde propanoylhydrazone and ferrocene carboxaldehyde furoylhydrazone that were derived from hydrazides,34 aromatic sulfonohydrazides, hydroxy phenyl hydrazide,35 N-[4-(diethylamino)benzylidine]-3-{[8-(trifluoromethyl) quinolin-4-yl]thio}propano hydrazide36 and 2-(2-hydrazinyl-1,6-dihydro-6-oxopyrimidin-4-yl)acetohydrazide,37 have been tested as potential corrosion inhibitors. Here, dicarbohydrazide compounds were chosen as inhibitors since it was clear from the literature that hydrazides efficiently decreased corrosion.
Hence, in this study, we report the synthesis of some novel dicarbohydrazide derivatives and evaluate them as effective corrosion inhibitors for N80 carbon steel in neutral corrosive media (i.e., 3.5% NaCl solution).
We investigated the synthesis and characterization of two novel hydrazides derivatives including ethanoanthracene-11,12-dicarbohydrazide derivatives N′11,N′12-bis((Z)-4-hydroxybenzylidene)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarbohydrazide (H2HEH) and N′11,N′12-bis((Z)-4-methoxybenzylidene)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarbohydrazide (H2MEH). They were tested as corrosion inhibitors of N80 steel in a 3.5% NaCl solution. Characterization methods used include potentiodynamic polarization (PP), electrochemical frequency modulation, EFM, and electrochemical impedance spectroscopy (EIS). In addition, X-ray photoelectron spectroscopy (XPS) was employed to verify the creation of an adsorbed protective film, discuss the mechanism of corrosion, and match the experimental data with the theoretical outcomes achieved from the density functional theory (DFT) calculations and Monte Carlo (MC) simulations.
Tafel polarization diagrams (PP) were achieved by modifying the potential values between 1100 to −200 mV SCE at a scan rate of 1 mV s−1. The Stern–Geary approach40 was employed for determining the corrosion current and was executed through the inferences of anodic and cathodic Tafel shapes of the charge transfer in the two directions. This was done to give a value that provides (logicorr) and equivalent corrosion potential (Ecorr) for the blank solution and each dose of the tested compounds. The icorr was applied to calculate the inhibition potency (η%) and surface covering (θ) by the equation below:
![]() | (1) |
Impedance measurements with an amplitude of 5 mV were carried out in the frequency range of 10 kHz to 0.1 Hz (peak-to-peak through ac signals at OCP).
The impedances were examined and constructed from the corresponding circuits (Fig. 5). The calculated variables from Nyquist plots were the charge transfer resistance (Rct) and the capacity of the double layer (Cdl). The inhibition prohibition (η%) and the surface coverage (θ) data were achieved utilizing the EIS technique and the values were determined according to the equation below:
![]() | (2) |
At frequencies of 2 and 5 Hz, EFM measurements were performed. Because the base frequency was 0.1 Hz, a wave was replicated in 1 second. The current responses, which were assigned to harmonious and intermodulation current peaks, were included in the intermodulation spectra. The icorr, Tafel slopes (βc and βa), and causality factors were estimated using stronger peaks (CF-2 and CF-3).40
Each electrochemical test was repeated 3 times to emphasize data duplicability.
The electrode potential was stabilized for 30 min prior to each trial. All trials were performed at 25 ± 1 °C. All evaluations were conducted on a Gamry Instrument Potentiostat/Galvanostat/ZRA. This comprised a Gamry framework system that was predicated on the ESA 400. Gamry techniques contained a DC105 for DC corrosion calculations, EIS 300 for EIS, and EFM 140 for EFM calculations. The instrument was connected to a computer for data gathering. The Echem analyst 6.25 software was applied for designing and fitting our data.
For MC simulations, the adsorption locator disclosed the proper adsorption formations of the protonated forms of the hydrazide derivatives by Monte Carlo investigations on Fe (1 1 0) exterior.43 This was to estimate the inhibition efficiency of the hydrazide derivatives. The adsorption of the hydrazide derivatives, water particles, and Fe (1 1 0) exterior was achieved in a simulation box (32.27 Å × 32.27 Å × 50.18 Å) within a periodic boundary tuning. Forcite classical simulation engine was applied to improve the particle energy of the hydrazides.44 The specifics of the relevant computations have been reported recently.41,44
(S3) shows the C13-NMR spectrum of H2MEH in d6-DMSO that supported the existence of the investigated hydrazide in tautomeric forms, as all signals are duplicated, revealing the existence of 34 carbon atoms, including two methylene groups at 38.60–40.33, four aliphatic methine groups at 44.90–47.41, four aliphatic methine groups at 45.3 and 46.6, two amidic carbon atoms (CO) at 171.60,170.60, two azomethine (C
N) groups at 169.1, 167.87 and eight aromatic methine groups from 123.20 to 143.34 ppm, respectively.
![]() | ||
Fig. 2 Open circuit diagrams (a, b) and Tafel plots (c, d) for the corrosion of N80 steel in 3.5% NaCl solution in the lack and existence of diverse concentrations of the synthesized hydrazides. |
Tafel curves are generally accepted to ensure suitable data on the kinetics of electrochemical corrosion variables. The presence of different concentrations of the prepared hydrazides changed each anodic plot and cathodic plot, as shown in Fig. 2c and d. These diminished the corrosion current density values, thereby creating a notable lowering in the corrosion rate values.
The anodic and cathodic current responses were reduced in the presence of compound I, as shown in Fig. 2. This influenced the expansions with the increase in the concentrations of H2HEH and H2MEH. The addition of H2HEH and H2MEH lowered the anodic dissolution of N80 specimens and delayed the cathodic oxygen reduction processes. The cathodic reaction in neutral solution (3.5% NaCl) consists of the reduction of oxygen into OH− ions:
This performance was assigned to the adsorption of the H2HEH and H2MEH inhibitors on the active spots of the studied N80 steel sample.
The corrosion kinetic variables, including the corrosion potential (Ecorr), anodic Tafel slope (βa), cathodic Tafel slope (βc) and corrosion current density (icorr) were acquired from the PP figures and the data indicated in Table 2. The inhibition proficiency (η%) was considered by eqn (1).49
Comp | Conc, M | −Ecorr, mV | icorr, μA cm−2 | βa, mV dec−1 | βc, mV dec−1 | C.R. mmy−1 | θ | η% |
---|---|---|---|---|---|---|---|---|
Blank | 0.00 | 915 | 113.0 ± 5.65 | 1512 | 152 | 51.46 | — | — |
H2HEH | 1 × 10−6 | 906 | 33.1 ± 2.31 | 999 | 142 | 15.12 | 0.707 | 70.7 |
5 × 10−6 | 954 | 30.4 ± 3.04 | 1026 | 139 | 13.87 | 0.731 | 73.1 | |
1 × 10−5 | 958 | 21.0 ± 1.95 | 1042 | 138 | 9.61 | 0.814 | 81.4 | |
5 × 10−5 | 931 | 15.4 ± 1.50 | 844 | 142 | 7.04 | 0.864 | 86.4 | |
1 × 10−4 | 902 | 8.8 ± 0.08 | 613 | 150 | 4.02 | 0.922 | 92.2 | |
H2MEH | 1 × 10−6 | 933 | 30.1 ± 2.65 | 1025 | 135 | 13.74 | 0.734 | 73.4 |
5 × 10−6 | 939 | 27.0 ± 2.70 | 883 | 133 | 12.32 | 0.761 | 76.1 | |
1 × 10−5 | 962 | 18.4 ± 1.20 | 956 | 127 | 8.39 | 0.837 | 83.7 | |
5 × 10−5 | 928 | 14.0 ± 0.96 | 757 | 144 | 6.41 | 0.876 | 87.6 | |
1 × 10−4 | 911 | 7.6 ± 0.07 | 524 | 182 | 3.45 | 0.933 | 93.3 |
In the presence of H2HEH and H2MEH, the corrosion rate reduced, as exhibited in Fig. 2. The compounds also inhibit the cathodic hydrogen evolution and anodic metal dissolution reactions.50–52 The changes in the values of βa and βc in the attendance of the compounds suggested the occurrence of the anodic metal dissolution and cathodic oxygen reduction processes. In the cathodic reaction, the inhibitor molecules were chemically adsorbed and retarded the O2 reduction, while in the anodic reaction, the inhibitor molecules were physically adsorbed and hindered the dissolution of N80 metal. Furthermore, the high value of the anodic Tafel slope (βa) is attributed to the oxide layer (passive layer) as a result of the oxygen existence in the solution that is more stabilized by the existence of inhibitors.53 The reactions were enhanced by the increase in the concentration of the compounds. A shift in the values of Ecorr at about 62 mV implied that the H2HEH and H2MEH compounds acted as mixed-type inhibitors.54 The values of icorr decreased from 113.0 to 7.6 mA cm−2 with the increase in the concentration of the compound. The inhibition efficacy was augmented to 93.3% owing to the adsorption of the inhibitors, which hindered the active sites on the N80 steel exterior. Additionally, the surface area that was accessible for Cl− ions was reduced.55
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Fig. 3 Nyquist plots for the corrosion of N80 steel in 3.5% NaCl solution without and with various diverse synthesized hydrazides (a) H2HEH and (b) H2MEH. |
![]() | ||
Fig. 4 Bode diagrams for the corrosion of N80 steel in 3.5% NaCl solution before and after adding altered doses of the synthesized hydrazides (a) H2HEH and (b) H2MEH. |
The Nyquist diagrams were examined to be single capacitive loops suited with a one-time constant (i.e., that seemed to be a single capacitive loop).56 The capacitive loop at the high-frequency area is assigned to the corrosion product/inhibitor film, and the capacitive loop at the middle-frequency area is assigned to the charge transfer reaction at the electrode/solution interface.57 The size of the capacitive loop was found to rise with concentrations of the H2HEH and H2MEH. This was ascribed to the enlargement in the surface that was covered by the examined inhibitors on the N80 steel sample exterior.58 To elucidate the frequency-independent phase change within the used alternating potential and current response, a constant phase element (CPE) was replaced by a double layer capacitance (Cdl). Additionally, phase angle vs. log frequency in Bode diagrams presenting two-phase crests are associated with the relaxation process of the electrical double layer capacitor and adsorbed H2HEH and H2MEH.59 Furthermore, an incessant increase in the phase angle at high frequencies with rising the H2HEH and H2MEH concentrations indicates the growth of the adsorbed layer on the N80 steel surface.60
The EIS measurements of the examined components were assayed through the corresponding model shown in Fig. 5, which provided a single charge transfer reaction. The model was discovered to be in fit accordance with the obtained experimental data. The CPE was included in this model as opposed to a Cdl to provide a more appropriate fitting.61 The Cdl that comprised a CPE exponent (Y0 and n) were used in the formula below:62
Cdl = Y0(ωmax)n−1 | (3) |
Table 3 provides the impedance evidence. The value of Rct increased with the increase in the concentrations of H2HEH and H2MEH, suggesting an upturn in the inhibition efficacy (η%).
Comp | Conc., M | Rf, Ω cm2 | Rct, Ω cm2 | CPE1 | CPE2 | Cdl, μF | θ | η% | ||
---|---|---|---|---|---|---|---|---|---|---|
Y0, μΩ−1 s cm−2 | n | Y0, μΩ−1 s cm−2 | n | |||||||
Blank | 0.00 | 130 | 565.5 ± 28.27 | 2.48 | 0.660 | 4.26 | 0.903 | 2.23 | — | — |
H2HEH | 1 × 10−6 | 223 | 1436 ± 71.8 | 1.17 | 0.653 | 2.08 | 0.917 | 1.23 | 0.606 | 60.6 |
5 × 10−6 | 254 | 1785 ± 124.9 | 1.64 | 0.669 | 1.60 | 0.710 | 0.15 | 0.683 | 68.3 | |
1 × 10−5 | 352 | 2705 ± 135.2 | 0.83 | 0.679 | 0.64 | 0.796 | 0.13 | 0.791 | 79.1 | |
5 × 10−5 | 466 | 3238 ± 226.6 | 0.48 | 0.664 | 0.50 | 0.804 | 0.10 | 0.825 | 82.5 | |
1 × 10−4 | 472 | 6745 ± 337.2 | 0.20 | 0.668 | 0.26 | 0.810 | 0.06 | 0.916 | 91.6 | |
H2MEH | 1 × 10−6 | 282 | 1889 ± 151.1 | 1.63 | 0.650 | 2.04 | 0.806 | 0.54 | 0.701 | 70.1 |
5 × 10−6 | 271 | 2012 ± 201.2 | 1.82 | 0.689 | 4.05 | 0.611 | 0.19 | 0.719 | 71.9 | |
1 × 10−5 | 368 | 3055 ± 183.3 | 0.92 | 0.700 | 1.40 | 0.689 | 0.12 | 0.815 | 81.5 | |
5 × 10−5 | 396 | 3875 ± 232.5 | 0.50 | 0.680 | 1.10 | 0.669 | 0.07 | 0.854 | 85.4 | |
1 × 10−4 | 560 | 7285 ± 364.3 | 0.27 | 0.681 | 0.60 | 0.666 | 0.04 | 0.922 | 92.2 |
The values of Cdl and Y0 diminished in the presence of the H2HEH and H2MEH, as can be seen from Table 3 and this reduction in the CPE/Cdl values was accompanied by a decrease in the local dielectric constants. The current situation is due to the exchange of water particles by H2HEH or H2MEH inhibitors by the adsorption process at the metal/acid interface, impeding the N80 steel corrosion.66,67
The intermodulation spectra acquired from EFM of the N80 steel corrosion in a 3.5% NaCl medium in the absence and presence of H2HEH and H2MEH are demonstrated in Fig. 6 and 7, respectively.
![]() | ||
Fig. 6 (A–F) Electrochemical frequency modulation spectra for the corrosion of N80 steel in a 3.5% NaCl medium in the lack and presence of different doses of the H2HEH at 25 °C. |
![]() | ||
Fig. 7 (A–F) Electrochemical frequency modulation spectra for the corrosion of N80 steel in a 3.5% NaCl medium in the absence and presence of altered doses of the H2MEH at 25 °C. |
Table 4 summarizes the values for the corrosion kinetic variables under study at various concentrations of H2HEH and H2MEH in 3.5% NaCl solution at 25 ± 1 °C (icorr, βa, βc, CF-2, CF-3, and η% calculated from eqn (1)). The corrosion current densities were reduced with the increase in the concentrations of the inhibitors. The inhibition prohibition was high at high concentrations of the H2HEH and H2MEH.
Comp | Conc, M | icorr, μA | βa (mV dec−1) | βc (mV dec−1) | C.R (mpy) | CF-2 | CF-3 | θ | η% |
---|---|---|---|---|---|---|---|---|---|
Blank | 0.00 | 132.4 ± 7.94 | 803 | 117 | 60.46 | 2.32 | 3.13 | — | — |
H2HEH | 1 × 10−6 | 40.2 ± 3.87 | 814 | 109 | 18.34 | 2.01 | 2.13 | 0.696 | 69.6 |
5 × 10−6 | 36.2 ± 2.87 | 868 | 103 | 16.83 | 2.37 | 2.74 | 0.727 | 72.7 | |
1 × 10−5 | 25.0 ± 2.14 | 815 | 131 | 11.42 | 2.39 | 3.41 | 0.811 | 81.1 | |
5 × 10−5 | 18.9 ± 1.32 | 820 | 136 | 8.670 | 1.89 | 3.33 | 0.857 | 85.7 | |
1 × 10−4 | 10.1 ± 1.01 | 893 | 103 | 4.596 | 1.70 | 3.18 | 0.924 | 92.4 | |
H2MEH | 1 × 10−6 | 36.7 ± 2.86 | 834 | 178 | 16.75 | 2.25 | 2.88 | 0.723 | 72.3 |
5 × 10−6 | 33.6 ± 3.36 | 821 | 132 | 15.32 | 2.26 | 3.19 | 0.746 | 74.6 | |
1 × 10−5 | 23.3 ± 1.89 | 829 | 142 | 10.66 | 1.87 | 3.12 | 0.824 | 82.4 | |
5 × 10−5 | 17.2 ± 1.32 | 816 | 128 | 7.856 | 2.40 | 2.85 | 0.870 | 87.0 | |
1 × 10−4 | 8.4 ± 0.84 | 824 | 139 | 3.828 | 2.23 | 2.45 | 0.937 | 93.7 |
The CF-2, CF-3 values are provided in Table 4. These values were not far from the expected values that were consistent with the EFM theory.69 The values coincided with the power of the Tafel slopes and the corrosion current densities. The CF-2 and CF-3 values in Table 4 show that the evaluated values were well attributed. The regular values for CF-2 and CF-3 were 2 and 3, accordingly. The diversion of causality factors from its perfect values was most likely a result of the disturbance amplitude, which was insufficient, or the frequency spectrum resolution was low. Additionally, the inhibition was not carried out appropriately. The inhibition efficiency assessed from PP, EIS and EFM was acceptable.
![]() | (4) |
Experiments were conducted to appropriate the experimental results to different isotherms involving Freundlich (R2 = 0.718, for H2HEH and R2 = 0.798 for H2MEH), Frumkin (R2 = 0.368, for H2HEH and R2 = 0.464 for H2HEH), Temkin (R2 = 0.799, for H2HEH and R2 = 0.789 for H2MEH) and Flory–Huggins (R2 = 0.842 for H2HEH and R2 = 0.889 for H2MEH). Most of the data followed the Langmuir adsorption isotherm as evidenced in Fig. 8.71
![]() | (5) |
![]() | ||
Fig. 8 Langmuir isotherm curve for N80 steel corrosion in 3.5% NaCl medium with different doses of the synthesized hydrazides at 25 °C. |
As shown in Fig. 8, the plot of C/θ against C showed a straight line with an adjusted coefficient of R2, nearly equal to unity. This revealed that H2HEH and H2MEH followed a Langmuir isotherm and there is a small connection within the adsorbed particles. Additionally, the , or free energy of adsorption, were assessed using the equation below:72
![]() | (6) |
The higher values of the adsorption constant suggested strong adsorption between H2HEH or H2MEH and the N80 steel surface. Moreover, values of −36.87 and −37.14 kJ mol−1 demonstrated the spontaneous adsorption of the synthesized hydrazides; thus, the adsorption types on the N80 steel exterior were physisorption and chemisorption.73
![]() | (7) |
![]() | ||
Fig. 9 Anodic and cathodic polarization plots for the corrosion of N80 steel in 3.5% NaCl solution in the lack and existence of 1 × 10−4 M concentration of the synthesized hydrazides. |
Temp, C° | Compound | −Ecorr, mV | icorr, μAcm−2 | βa, mV dec−1 | βc, V dec−1 | C.R. mmy−1 | θ | η% |
---|---|---|---|---|---|---|---|---|
25 | Blank | 915 | 113.0 | 1512 | 152 | 51.46 | — | — |
H2HEH | 902.0 | 8.8 | 613 | 150 | 4.02 | 0.877 | 87.7 | |
H2MEH | 911.0 | 7.6 | 524 | 182 | 3.45 | 0.922 | 92.2 | |
30 | Blank | 925.0 | 126.0 | 700 | 134 | 57.33 | — | — |
H2HEH | 914.0 | 14.1 | 536 | 154 | 6.44 | 0.788 | 78.8 | |
H2MEH | 919.0 | 10.6 | 1858 | 158 | 4.86 | 0.841 | 84.1 | |
40 | Blank | 893.0 | 161.0 | 233 | 123 | 73.42 | — | — |
H2HEH | 914.0 | 18.6 | 511 | 149 | 8.49 | 0.729 | 72.9 | |
H2MEH | 900.0 | 13.6 | 210 | 130 | 6.19 | 0.790 | 79.0 | |
50 | Blank | 915.0 | 189.0 | 244 | 115 | 86.33 | — | — |
H2HEH | 899.0 | 20.4 | 177 | 117 | 9.32 | 0.729 | 72.9 | |
H2MEH | 885.0 | 15.8 | 196 | 129 | 7.23 | 0.790 | 79.0 |
By designing (logk) versus (1/T), the values of
were acquired from the previous equation:
(Fig. 10). The activation energy for the corrosion of N80 C-steel in 3.5% NaCl corrosive solution increased in the attendance of H2HEH and H2MEH (Table 7). The increase in
suggested a structure of energy obstruction. The rate augments in the existence of the inhibitors were higher than those in the absence of corrosive media. Thus, the prohibition tendency of H2HEH and H2MEH lessened with a rise in the temperature.
![]() | ||
Fig. 10 log![]() |
The above outcomes supported the physical nature of the adsorption of H2HEH and H2MEH on an N80 steel surface. The rise in the temperature decreased the number of adsorbed particles, thus, decreasing the inhibition efficiency. The inhibitors prevent the corrosion process by increasing the activation energy. The adsorption process on the N80 steel exterior was by a charge transfer mechanism. These inhibitors also serve as building blocks for mass. Furthermore, the rather small activation energy values for H2HEH and H2MEH implied a physical adsorption mechanism.
The change of entropy (ΔS*) and change of enthalpy (ΔH*) were calculated utilizing the equation below:
![]() | (8) |
![]() | ||
Fig. 11 log![]() |
![]() | ||
Fig. 13 XPS outlines of C 1s, Cl 2p, Fe 2p, O 1s, N 1s, and Na 1s for N80 steel in 3.5% NaCl treated with 1 × 10−4 M of H2MEH. |
N80 steel in 3.5% NaCl treated with 1 × 10−4 M H2MEH | ||
---|---|---|
Core element | BE, eV | Assignments |
C 1s | 285.51 | –C–H, –C–C–, –C![]() |
287.55 | –C–O | |
289.36 | –C![]() |
|
Cl 2p | 198.66 | Cl 2p3/2 |
199.78 | Cl 2p1/2 | |
Fe 2p | 707.23 | Fe 2p3/2 of Fe0 |
711.20 | Fe 2p3/2 of Fe2+ in FeO, FeCl2 | |
714.06 | Fe 2p3/2 of Fe3+ in Fe2O3, Fe3O4, FeOOH | |
720.26 | Satellite Fe 2p3/2 of Fe2+ in FeO | |
724.71 | Fe 2p1/2 of Fe2+ in FeO | |
727.91 | Fe 2p1/2 of Fe3+ in Fe2O3 | |
733.48 | Satellite Fe 2p1/2 of Fe2+ in Fe2O3, Fe3O4 | |
O 1s | 530.14 | FeO, Fe2O3 |
531.80 | FeOOH | |
536.03 | Adsorbed water molecules | |
N 1s | 399.94 | –C![]() |
401.07 | –C![]() |
|
Na 1s | 1072.15 | Na in NaCl |
The involved spectra of C 1s displayed three peaks (Fig. 13), including that for the inhibited N80 steel at 285.51, which was assigned to –C–C–, –CC–, and C–H bonds. The 287.19 eV and 289.36 eV peaks are ascribed to –C–O, and –C
N+ bonds, respectively.75,76 The deconvolution of the Cl 2p spectra divulged into two peaks (Fig. 13) at 198.6 and 199.78 eV, which were assigned to Cl 2p3/2 and Cl 2p1/2, respectively.77 The XPS spectra of Fe 2p showed seven peaks (Fig. 13) at 707.23 eV for Fe 2p3/2 of Fe0, 711.20 eV for Fe 2p3/2 of Fe2+, 714.06 eV for Fe 2p3/2 of Fe3+,77 720.01 eV for Fe 2p3/2 satellites of Fe2+,78 724.36 eV for Fe 2p1/2 of Fe2+, 727.91 eV for Fe 2p1/2 of Fe2+, and 733.48 eV for Fe 2p1/2 satellites of Fe2+.79,80 Furthermore, the high-resolution O 1s spectrum showed three peaks (Fig. 13), including 530.14 eV for O2− that interacted with Fe2+and Fe3+ to form FeO and Fe2O3 oxides.81,82 The 531.80 and 536.03 eV were for the OH− that interacted with Fe3+ to form FeOOH and adsorbed water molecules, respectively.83,84
The N80 steel treated with H2MEH in 3.5% NaCl exhibited two N 1s peaks (Fig. 13) at 399.94 and 401.75 eV, which were ascribed to –CN and –C
N+ bonds, respectively. These were due to the H2MEH molecules.85,86 Finally, a distinctive Na 1s peak (Fig. 13) observed at 1072.15 eV was assigned to Na in the NaCl solution.87 These results verified the adsorption of H2MEH on the N80 steel exterior. These compound created a durable shielding layer.
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Fig. 14 The optimized molecular constructions, HOMO and LUMO for the synthesized hydrazides via the DMol3 module. |
Compound | H2HEH | H2MEH |
---|---|---|
EHOMO, eV | −5.26 | −4.86 |
ELUMO, eV | −2.68 | −2.95 |
ΔE, eV | 2.58 | 1.91 |
I | 5.26 | 4.86 |
A | 2.68 | 2.95 |
χ | 3.97 | 3.91 |
η | 1.29 | 0.96 |
σ | 0.78 | 1.05 |
ΔN | 1.18 | 1.21 |
Dipole moment, debye | 7.04 | 7.20 |
Molecular surface area, Å2 | 498.89 | 553.87 |
The energy gap (ΔE) is an essential element to assist the inhibition potency of the hydrazides for corrosion. Lower ΔE values suggested better inhibition potencies.89 As evidenced in Table 9, H2MEH has a lower ΔE value (1.91 eV) than H2HEH (2.58 eV). This implied a higher tendency for H2MEH adsorption on a C-steel exterior. The smaller values of electronegativity (χ) for H2MEH suggested the stronger ability of H2MEH than H2HEH to provide electrons to the metal.90 The stability and reactivity of a compound could also be used to evaluate its hardness (η) and softness (σ). Soft compounds are highly reactive than hard compounds and they effortlessly provide electrons to an N80 sample during the adsorption. Thus, they work as effective corrosion inhibitors.91 As shown in Table 9, the H2MEH has a higher σ value (1.05) and H2HEH has a lower η value (0.96). This indicated the ability of H2MEH to easily provide electrons to the examined sample. This produced a high prohibition potency.
The ΔN values showed the tendency of a particle to donate electrons to the surface. A high ΔN value, suggests a larger electron-donating ability of an inhibitor. It has been found that when ΔN < 3.6, the prohibition performance was enhanced because of the high electron-contributing ability.92 Table 9 lists the calculated values of ΔN. The higher ΔN values for H2MEH (1.21) than for H2HEH (1.18) suggested that H2MEH had a higher tendency to donate electrons to the examined sample.
The dipole moment is a vigorous element that confirms a corrosion prohibition.93 A rise in a dipole moment suggests an improvement in the deformation energy and enhancement in the adsorption of an inhibitor on the steel surface. Thus, a rise in the dipole moment will increase the prohibition efficacy.94 As shown in Table 9, the dipole moment of H2MEH (7.20 debye) is higher than H2HEH (7.04 debye). This verified the higher tendency for H2MEH adsorption on the N80 surface, causing an improved prohibition potency.
Additionally, a visible correlation was found between the molecular surface area of the hydrazides and their tendency to protect the N80 surface in a 3.5% NaCl medium. A larger surface area improves the prohibition potency since the contact area on the N80 surface becomes larger for the hydrazides.95 As shown in Table 9, H2MEH showed a larger molecular surface area (553.87 Å2), thus, it provided a better prohibition potency than H2HEH.
The MEP mapping in a 3D visual device is designed to recognize the optimum electrostatic result, which is calculated over a particle from the total charge dispersion.96 In the MEP maps shown in Fig. 15, the red regions delineated the greatest electron density, where MEP is the most negative (nucleophilic reaction). Meanwhile, the blue regions delineate from the highest positive area (electrophilic reaction).97 The photograph in Fig. 15 shows the most negative areas were from hydrazide at the methoxy, hydroxy and carbonyl rings. Nevertheless, a lower density at the phenyl rings was observed. The red spots with high electron density in the hydrazides were the suitable connections on the N80 surface for building an adsorbed protective film.
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Fig. 16 The adsorption locator module achieved the maximal suitable conformation for the adsorption of the synthesized hydrazides on Fe (1 1 0) substrate. |
Structures | Adsorption energy/kcal mol−1 | Rigid adsorption energy/kcal mol−1 | Deformation energy/kcal mol−1 | dEads/dNi:inhibitor/kcal mol−1 | dEads/dNi:water/kcal mol−1 |
---|---|---|---|---|---|
a The energy of the metal adsorbate arrangement, where the energy of the adsorbates was neglected is elucidated by dEads/dNi values.100 The dEads/dNi values for H2MEH was −194.77 kcal mol−1, which was higher than the value for H2HEH molecules of −178.65 kcal mol−1, which affirmed stronger adsorption of H2MEH than H2HEH. Besides, the dEads/dNi value for water molecules is 13.81 kcal mol−1, suggesting the stronger adsorption of hydrazides than water. Hence, the hydrazides were conclusively adsorbed on the N80 surface and formed an effective protective barrier. | |||||
Fe (1 1 0) | −2636.23 | −2756.00 | 119.77 | −178.65 | −13.73 |
H2HEH | |||||
Water | |||||
Fe (1 1 0) | −2649.11 | −2771.19 | 122.08 | −194.77 | −13.88 |
H2MEH | |||||
Water |
(a) There were interactions between H2HEH or H2MEH and the substrate.
(b) The investigated molecules combined on the metal layer.
(c) There were chemical processes involved.
(d) The electrode potentials were relevant.
(e) The doses of the examined inhibitors were relevant.
(f) The temperature of the system was important.
(g) The characteristics of the metal exterior were important.
The adsorption of the synthesized H2HEH and H2MEH on the N80 steel metal can occur instantly by virtue of donor–acceptor correlations with N or O atoms of the compounds and the presence of free d- orbitals in N80 steel particles.
The H2HEH and H2MEH, including their electronegative atoms, were frequently reported to have a large ability to contribute electrons to an N80 steel surface.49 Thus, the interaction between H2HEH and H2MEH and the exterior of the N80 steel involved the electronegative atoms of the inhibitors. The localities of higher electron density are common spots for electrophiles attack. Therefore, N and O atoms with energetic sites, have the greatest capability to bond with the N80 steel exterior.
The prohibition tendency of H2MEH was better than that of H2HEH.
H2MEH provided a higher inhibition efficiency percentage, which was a result of the existence of p-OCH3, which is an electron-contributing group in its structure. This group increased the electron charge density on the inhibitor. The lower efficiency in H2HEH was due to the H-atom in the p-position, which has no purpose in the charge density of the compound.
In conclusion, the sites with electron-donating groups (–N and –O atoms) were the most likely spots for bonding of H2HEH and H2MEH on the metal surface. Additionally, the findings from quantum chemical calculations provided excellent matching with the collected data from the electrochemical techniques and adsorption of the synthesized compounds. These findings were mostly focused on the relevance of nitrogen and oxygen atoms.
Finally, Table 11 demonstrates a comparison between our results and previously the published studies on corrosion inhibition utilizing hydrazide derivatives in different corrosive mediums.
Inhibitor used | Examined metal | Corrosive media | Inhibition efficiency | Reference |
---|---|---|---|---|
Ferrocene Schiff bases derived from hydrazides | Mild steel | In 0.5 M, H2SO4 | 91.1% EIS | 102 |
Sulfonohydrazide derivatives | XC38 carbon steel | 1 M HCl | 91.9% polarization, 93.1% EIS | 34 |
Hydroxy phenyl hydrazides | Mild steel | 1 M HCl solution | 92.41% EIS, 92.4% weight loss | 35 |
Cationic Gemini surfactant | X-65 steel | 1.0 M HCl | 91.44% EIS, 94.73% EIS | 103 |
Organic acid hydrazides | Mild steel | 1.0 M HCl | 93.8% weight loss, 81.3% polarization | 32 |
2-(2-Hydrazinyl-1,6-dihydro-6-oxopyrimidin-4-yl) acetohydrazide | Mild steel | M HCl and 0.5 M H2SO4 | 89.8% polarization in HCl, 88.5% polarization in H2SO4 | 37 |
Polymeric hydrazide derivatives | Mild steel | 1 M HCl | 93.97% polarization | 104 |
Novel dicarbohydrazide derivatives | N80 steel | 3.5% NaCl solution | 93.3% polarization, 92.2% EIS | Our current study |
(1) Data collected from the electrochemical methods and theoretical calculations indicated that the synthesized hydrazides served as powerful compounds for N80 carbon steel corrosion in a 3.5% NaCl solution.
(2) Prohibition tendency enhanced with the rise in the concentration of the examined hydrazides. It decreased with an increase in the temperature.
(3) The prohibition efficiency, which was measured using PP, EIS and EFM was in a respectable arrangement.
(4) PP measurements showed that the synthesized hydrazides behaved as a mixed-type inhibitor.
(5) XPS studies affirmed the formation and creation of a durable shielding layer, which protected the exterior of the N80 carbon steel from corrosion.
(6) The synthesized hydrazides were adsorbed on the N80 carbon steel surface in a 3.5% NaCl corrosive medium. The adsorption was an exothermic process, which indicated both physisorption and chemisorption, and followed the Langmuir adsorption isotherm.
(7) These findings demonstrate the superior performance of the prepared H2HEH and H2MEH hydrazide derivatives as inhibitors for N80 carbon steel corrosion and accordingly prove their favorability for the protection of steel in aggressive chloride solutions. Due to the unique structure of these compounds, they can be applied as effective inhibitors during the acid pickling process.
Footnote |
† Electronic supplementary information (ESI) available. See https://doi.org/10.1039/d2ra01751b |
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