Assessment of New Imidazol Derivatives and Investigation of Their Corrosion-Reducing Characteristics for Carbon Steel in HCl Acid Solution

Round 1

Reviewer 1 Report

 

Comments

This manuscript presents a combined experimental and simulation study that investigates the inhibitory effect of three classes of imidazole derivatives, namely 5-((2,4,5-triphenyl-1H-imidazol-1-yl)methyl)quinolin-8-ol (TIMQ) and 5-((2-(4-chlorophenyl)-4,5-diphenyl-1H-imidazol-1-yl)methyl)quinolin-8-ol (CDIQ), on the corrosion behavior of carbon steel (CS) specimens in an HCl medium. The inhibition efficiencies of different inhibitor concentrations were evaluated through weight loss tests, electrochemical methods, and polarization studies. The study also highlights the significance of quantum chemical descriptors, such as global and local chemical reactivity, in explaining the similar inhibition efficiencies observed for TIMQ and CDIQ inhibitors, which is consistent with the experimental data. Furthermore, molecular dynamic simulations were conducted to analyze the adsorption process of the proposed inhibitors onto the CS surface. To ensure the publication of the manuscript, the following issues need to be addressed.

1. Has any conformer search been performed for conformational sampling before conducting the DFT calculations? Considering that TIMQ and CDIQ may have different potential conformers, employing configuration screening packages like Molclus (http://www.keinsci.com/research/molclus.html) and CREST (https://crest-lab.github.io/crest-docs/) can enhance the accuracy of the calculations.

2. It is suggested to use dispersion correction to improve the accuracy of structure optimizations and other calculations.

3. Can the authors provide more information on using ChemAxon and Marvin to obtain the microspecies of these inhibitors as a function of pH? Specifically, do they require the DFT optimized structures or energies as input?

4. ESP (Electrostatic Potential) needs to be provided with the full name, similar to MEP (Molecular Electrostatic Potential), FMO (Frontier Molecular Orbitals), and MDS (Molecular Dynamic Simulations?).

5. The electrostatic potential-mapped molecular van der Waals (vdW) surface shown in Figure 13 is generated based on the isosurface density of an unknown parameter. The details should be provided. Additionally, it is suggested to use the wavefunction analysis software Multiwfn instead of GaussView for electrostatic potential analysis, as it provides more details such as local minima and maxima of the ESP surface and the global maxima and minima on the surface. This would enhance the quality of the discussion.

6. In the molecular dynamics simulations, the system with (500H₂O, 5H₃O⁺, 5Cl^-, and imidazol analogs) is utilized. Is there any experimental value available to benchmark the choice of this ratio for each species? It would be interesting to know if there are concerns about having too many water molecules in the simulation box, which might push CDIQ and TIMQ away from aqueous phase onto the Fe(110) surface.

7. In Figures 17-18, the atom type should be specified in the figure caption.

 

Author Response

Dear Editor-in-Chief,

We are pleased to inform you that based on the reviews; we have prepared the revised

Manuscript ID: coatings-2525840 R1and the rebuttal letter as a sign of positive response to the comments of your respected reviewers. We have carefully implemented all comments to improve the quality of our revised manuscript. To make it easier for you and reviewers, we have indicated the changes, corrections and additions in red color. In response to reviewer’s comments letter, we reproduced each comment by heading “Reviewer’s comment” and our responses have been given by heading “Author’s response”. We would like your final decision on our revised document for possible publication in the journal of coating in the special issue “Theoretical and Experimental Assessments of Corrosion Inhibitors”.

We appreciate your consideration of our manuscript, and we look forward to hearing from you soon. Any further information and suggestions are greatly appreciated.

Thank you very much for your consideration.

With best regards, Yours sincerely,

Dr. Fouad BENHIBA

 

Reviewer 1

Comments

This manuscript presents a combined experimental and simulation study that investigates the inhibitory effect of three classes of imidazole derivatives, namely 5-((2,4,5-triphenyl-1H-imidazol-1-yl)methyl)quinolin-8-ol (TIMQ) and 5-((2-(4-chlorophenyl)-4,5-diphenyl-1H-imidazol-1-yl)methyl)quinolin-8-ol (CDIQ), on the corrosion behavior of carbon steel (CS) specimens in an HCl medium. The inhibition efficiencies of different inhibitor concentrations were evaluated through weight loss tests, electrochemical methods, and polarization studies. The study also highlights the significance of quantum chemical descriptors, such as global and local chemical reactivity, in explaining the similar inhibition efficiencies observed for TIMQ and CDIQ inhibitors, which is consistent with the experimental data. Furthermore, molecular dynamic simulations were conducted to analyze the adsorption process of the proposed inhibitors onto the CS surface. To ensure the publication of the manuscript, the following issues need to be addressed.

1. Has any conformer search been performed for conformational sampling before conducting the DFT calculations? Considering that TIMQ and CDIQ may have different potential conformers, employing configuration screening packages like Molclus (http://www.keinsci.com/research/molclus.html) and CREST (https://crest-lab.github.io/crest-docs/) can enhance the accuracy of the calculations.

Author response: We agree with the reviewer comment, but unfortunately, the structures of the investigated inhibitors were drawn using gauss view program without looking for possible conformational structures. Since we use DFT calculations implemented in Gaussian 09, is it not easy to look for all the conformational structures with high basis set, since the molecules are not small. This can be carried out by using DFT method (dmol3) implemented in material studio.

2. It is suggested to use dispersion correction to improve the accuracy of structure optimizations and other calculations.

Author response: This is a very good and an interesting question, However, Dispersion (van der Waals) interaction plays a crucial role in the formation, stability, and function of molecules and materials. As known, computational methods based on approximations to density functional theory (DFT) have the potential to provide computationally efficient approaches to modelling systems in which non-covalent interactions play a central role. A critical deficiency of conventional DFT approximations is their well-known inability to accurately and reliably model non-covalent (especially dispersion) interactions. In the current study, we are not dealing with hydrogen bonding interactions or other possible van de Waal interactions between two the molecules (synergistic effect) and we are treated the isolated molecules. In case of studying the synergetic effect, this point will be taken into account. 

3. Can the authors provide more information on using ChemAxon and Marvin to obtain the microspecies of these inhibitors as a function of pH? Specifically, do they require the DFT optimized structures or energies as input?

Author response: no they don’t DFT calculation. The Calculator Plugins are modules of Chemaxon's Marvin and JChem cheminformatics platforms and can be used to calculate physicochemical properties from chemical structures. Most molecules contain some specific functional groups likely to lose or gain proton(s) under specific circumstances. Each equilibrium between the protonated and deprotonated forms of the molecule can be described with a constant value called pK_a. The pK_a Plugin calculates the pK_a values of the molecule based on its partial charge distribution.

4. ESP (Electrostatic Potential) needs to be provided with the full name, similar to MEP (Molecular Electrostatic Potential), FMO (Frontier Molecular Orbitals), and MDS (Molecular Dynamic Simulations?).

Author response: All abbreviations have been revised and corrected.

5. The electrostatic potential-mapped molecular van der Waals (vdW) surface shown in Figure 13 is generated based on the isosurface density of an unknown parameter. The details should be provided. Additionally, it is suggested to use the wavefunction analysis software Multiwfn instead of GaussView for electrostatic potential analysis, as it provides more details such as local minima and maxima of the ESP surface and the global maxima and minima on the surface. This would enhance the quality of the discussion.

Author response: More details have been included in the revised manuscript. The suggestion of using Multiwfn instead of Gauss view  is useful for small molecules but in our case and as our molecules are somewhat large molecules, it is highly cost to calculate the isosurfaces using Multiwfn program. In addition, our study aims to in identify in a qualitative picture the negative and positive regions, which responsible for electrophilic and nucleophilic attacks with the metal surfaces. We have provided a numeral value for the active centres by calculated the condensed Fukui function, which gives us quantitively information about the reactivity of the electrophilic and nucleophilic centres as shown in Figure 16 and Table 8.

6. In the molecular dynamics simulations, the system with (500H₂O, 5H₃O⁺, 5Cl^-, and imidazol analogs) is utilized. Is there any experimental value available to benchmark the choice of this ratio for each species? It would be interesting to know if there are concerns about having too many water molecules in the simulation box, which might push CDIQ and TIMQ away from aqueous phase onto the Fe(110) surface.

Author response: The choice of the number of hydroxyl ions, chloride ions and water molecules in the molecular dynamics simulation is made taking into account electro neutrality, i.e. the same number of Cl^- and H₃O⁺ ions. Moreover, the choice of the number of particles is also made taking into account the volume of the simulation cell (suitable volume).

You should review more related work and cite them. For example

Ref: https://doi.org/10.1016/j.molliq.2017.04.124

7. In Figures 17-18, the atom type should be specified in the figure caption.

Author response: Action taken -Honorable reviewer, please see the Figures 17 and 18 thank you.

Reviewer 2 Report

This paper aims to evaluate the inhibition potential of imidazole derivatives against carbon steel in an HCl medium. The work is interesting and I would like to recommend it after some improvements.

1. The introduction should be better elaborated; this work must be linked to similar works to be able to better highlight the difficulty faced here.

2. Each abbreviation or acronym should be defined when it first appears.

3. It is not clear in Fig8, you say have a straight line with a correlation coefficient close to 1, but how could it be otherwise? A straight line always passes through two points. Please take a look at this graph.

4. As far as adsorption is concerned, the Langmuir model alone cannot explain such a phenomenon given the complexity of the molecules, this part seems overlooked.

5. Even if these organic inhibitors were deposited on the surface of the steel, you should perform the leaching tests in different environments to evaluate the eventual take-off.

6. Instead of speaking in this document of the HCl concentration which is not varied elsewhere, it would be more useful to specify the pH.

7. The plot in Figure 11 is confusing; the redshift you are referring to is for which peak? Why is there rather a shift in the spectrum, it looks like you don't have the same Baseline.

Author Response

Response to Comments of Reviewers

 

Dear Editor-in-Chief,

We are pleased to inform you that based on the reviews; we have prepared the revised

Manuscript ID: coatings-2525840 R1and the rebuttal letter as a sign of positive response to the comments of your respected reviewers. We have carefully implemented all comments to improve the quality of our revised manuscript. To make it easier for you and reviewers, we have indicated the changes, corrections and additions in red color. In response to reviewer’s comments letter, we reproduced each comment by heading “Reviewer’s comment” and our responses have been given by heading “Author’s response”. We would like your final decision on our revised document for possible publication in the journal of coating in the special issue “Theoretical and Experimental Assessments of Corrosion Inhibitors”.

We appreciate your consideration of our manuscript, and we look forward to hearing from you soon. Any further information and suggestions are greatly appreciated.

Thank you very much for your consideration.

With best regards, Yours sincerely,

Dr. Fouad BENHIBA

 

Reviewer 2

Comments and Suggestions for Authors

This paper aims to evaluate the inhibition potential of imidazole derivatives against carbon steel in an HCl medium. The work is interesting and I would like to recommend it after some improvements.

1. The introduction should be better elaborated; this work must be linked to similar works to be able to better highlight the difficulty faced here.

Author response: Action taken -Honorable reviewer please see Table 1, thank you.

2. Each abbreviation or acronym should be defined when it first appears.

Author response: Action taken -Honorable reviewer, thank you.

3. It is not clear in Fig8, you say have a straight line with a correlation coefficient close to 1, but how could it be otherwise? A straight line always passes through two points. Please take a look at this graph.

Author response: Action taken -Honorable reviewer see Figure 8.

4. As far as adsorption is concerned, the Langmuir model alone cannot explain such a phenomenon given the complexity of the molecules, this part seems overlooked.

Author response: Action taken -Honorable reviewer the plots of Cinh/θ v/s Cinh show linear plot for M HCl which indicate that the adsorption isotherm follows Langmuir. In addition, the adsorption reaction involves the formation of unimolecular layer with a constant energy of adsorption. Langmuir isotherm points to homogeneous adsorption over the metal surface, wherein the inhibitor molecule has constant enthalpies and adsorption activation energy.

5. Even if these organic inhibitors were deposited on the surface of the steel, you should perform the leaching tests in different environments to evaluate the eventual take-off.

Author response: That's right, leaching tests can be used to determine how long organic inhibitors last and how stable they are in various situations. This data is critical for determining the inhibitors' long-term efficiency in preventing corrosion of the steel by identifying the possibility for the inhibitors to leach off or deteriorate over time. Unfortunately, in our case, we can't carry out these tests because we don't have sufficient quantities of these synthesised inhibitors to do all these tests. Thank you for your understanding.

6. Instead of speaking in this document of the HCl concentration which is not varied elsewhere, it would be more useful to specify the pH.

Author response: When examining the inhibition of steel corrosion in a certain environment, mentioning the pH value would indeed give more valuable information. The corrosivity or reactivity of the system may not be accurately reflected by the HCl concentration alone. The pH number, on the other hand, offers a more thorough understanding of the solution's acidity or alkalinity, which can significantly affect how steel corrodes. While higher pH values are linked to greater corrosion resistance in alkaline conditions, lower pH values in acidic situations often suggest higher corrosion rates. Researchers can more accurately assess the effectiveness of corrosion inhibitors in preventing steel corrosion under particular circumstances by defining the pH. Generally, for a concentration of 1 M HCl, we consider that the pH of the medium is less than or equal to 0. The addition of an organic inhibitor with a low concentration has practically no influence on the pH of our medium.

7. The plot in Figure 11 is confusing; the redshift you are referring to is for which peak? Why is there rather a shift in the spectrum, it looks like you don't have the same Baseline.

Author response: you're absolutely right, thank you very much for your remark, the error has been rectified.

Reviewer 3 Report

Thank you for allowing me to review your manuscript. It is extremely long, and it reads almost like a report to a sponsor (money person) where you want to show how much work you did. For a scientific publication you only need to show the results that backs the message you want to deliver.

You present a series of data, showing this is higher that is lower but at the end what is the takeaway message? How much better are your two inhibitors compare to dozen of other inhibitors studied? Are your inhibitors good only for carbon steel in 1M HCl? Before conclusions you may add a paragraph with recommendations and outlook based on your expert knowledge. What in new in your manuscript that has not been discussed before? We need a little context if possible. 

Your manuscript needs to be edited by a professional technical writer. There are too many bad sentences everywhere. For example "Figures 9 and 10 shows data showing that", "steel metallic", or in Conclusions "inhibitors are almost have the same", etc. Instead of "non-existence" use absence? 

In the abstract you call your inhibitors "potent", but this word does not appear anywhere else. Why just before the Experimental the inhibitors are called "dyes"? 

You write that the study was done using "different" and "various" concentrations of the inhibitors. This is too vague and uninformative. Better say that the study was done in five concentrations of the inhibitors (including zero). 

Many figures (e.g., 2, 3, 4, 5, etc.) uses different symbols and colors to denote the same thing, for example the same concentration of inhibitors. This will be very confusing to a future reader. 

In the first paragraph of section 3.2, you say that the diameter of the impedance of two "investigated" molecules ... is higher, etc. The impedance is of the steel specimen, not of the molecules. When discussing the Bode plots you mention that the fact that the Rs was the same is because the "corrosive behavior" was the same. This is not true. Same Rs says that the conductivity of the electrolytes is the same. It does not say anything about their corrosive behavior. 

You mention that 1 mM i(E-03M) was the optimum concentration. How do you know? This was the highest concentration tested. That's all. 

Figures 9 & 10 show images of some corroded steel electrode. Is this the electrode after the PDP curve? It is unclear from the manuscript. Why the photographs are identical in Fig. 9 and 10? The caption of these two figures is very unclear. Not sure what "electrode only" means. 

The conclusions says that "three classes of imidazole derivatives" were tested, but this reviewer only found two. It also says the weight loss was used but this reviewer could not find data for weight loss. This manuscript has over ten authors and no one did proofreading before uploading for review.

What is "reactivity attacks" mentioned only in Conclusions? 

In Ref. 45 there is an extra x? Is this the Ralph G Pearson?  Is this a wrong reference? the initials do not match. How many other mistakes in references? 

 

 

This manuscript needs to be edited by a professional technical writer. Construction of sentences are not right, the humble "carbon steel" needs to be called but its proper name "carbon steel" or "CS". When you are discussion your material (not something that is in the literature) there are too many other names given to CS, for example "steel metallic" "steel" "steel electrodes",  "steel surfaces", "iron metal", "metallic bulk", etc. 

Author Response

Response to Comments of Reviewers

 

Dear Editor-in-Chief,

We are pleased to inform you that based on the reviews; we have prepared the revised

Manuscript ID: coatings-2525840 R1and the rebuttal letter as a sign of positive response to the comments of your respected reviewers. We have carefully implemented all comments to improve the quality of our revised manuscript. To make it easier for you and reviewers, we have indicated the changes, corrections and additions in red color. In response to reviewer’s comments letter, we reproduced each comment by heading “Reviewer’s comment” and our responses have been given by heading “Author’s response”. We would like your final decision on our revised document for possible publication in the journal of coating in the special issue “Theoretical and Experimental Assessments of Corrosion Inhibitors”.

We appreciate your consideration of our manuscript, and we look forward to hearing from you soon. Any further information and suggestions are greatly appreciated.

Thank you very much for your consideration.

With best regards, Yours sincerely,

Dr. Fouad BENHIBA

Reviewer 3

Comments and Suggestions for Authors

Thank you for allowing me to review your manuscript. It is extremely long, and it reads almost like a report to a sponsor (money person) where you want to show how much work you did. For a scientific publication you only need to show the results that backs the message you want to deliver.

You present a series of data, showing this is higher that is lower but at the end what is the takeaway message? How much better are your two inhibitors compare to dozen of other inhibitors studied? Are your inhibitors good only for carbon steel in 1M HCl? Before conclusions you may add a paragraph with recommendations and outlook based on your expert knowledge. What in new in your manuscript that has not been discussed before? We need a little context if possible. 

Author response: Thank you for these very helpful comments, action taken -Honorable reviewer please see the manuscript  (Table 1, introduction ,before conclusion)

Your manuscript needs to be edited by a professional technical writer. There are too many bad sentences everywhere. For example "Figures 9 and 10 shows data showing that", "steel metallic", or in Conclusions "inhibitors are almost have the same", etc. Instead of "non-existence" use absence? 

Author response:  Action taken -Honorable reviewer please see the manuscript.

In the abstract you call your inhibitors "potent", but this word does not appear anywhere else. Why just before the Experimental the inhibitors are called "dyes"? 

Author response:  Action taken, thank you.

You write that the study was done using "different" and "various" concentrations of the inhibitors. This is too vague and uninformative. Better say that the study was done in five concentrations of the inhibitors (including zero). 

Author response:  Action taken, thank you.

Many figures (e.g., 2, 3, 4, 5, etc.) uses different symbols and colors to denote the same thing, for example the same concentration of inhibitors. This will be very confusing to a future reader. 

Author response:  Action taken, thank you.

In the first paragraph of section 3.2, you say that the diameter of the impedance of two "investigated" molecules ... is higher, etc. The impedance is of the steel specimen, not of the molecules. When discussing the Bode plots you mention that the fact that the Rs was the same is because the "corrosive behavior" was the same. This is not true. Same Rs says that the conductivity of the electrolytes is the same. It does not say anything about their corrosive behavior. 

Author response:  Action taken, thank you.

You mention that 1 mM i(E-03M) was the optimum concentration. How do you know? This was the highest concentration tested. That's all. 

Author response:  The concentration range used in this work is chosen in accordance with the literature under the same experimental conditions. In addition, we apply the definition that the lower the concentration, the more effective the inhibitor. Consequently, the 4 concentrations used show that 10-3M is the most effective.

Figures 9 & 10 show images of some corroded steel electrode. Is this the electrode after the PDP curve? It is unclear from the manuscript. Why the photographs are identical in Fig. 9 and 10? The caption of these two figures is very unclear. Not sure what "electrode only" means. 

Author response:  Action taken, thank you.

The conclusions says that "three classes of imidazole derivatives" were tested, but this reviewer only found two. It also says the weight loss was used but this reviewer could not find data for weight loss. This manuscript has over ten authors and no one did proofreading before uploading for review.

Author response:  Action taken, thank you.

What is "reactivity attacks" mentioned only in Conclusions? 

Author response:  Action taken, thank you.

In Ref. 45 there is an extra x? Is this the Ralph G Pearson?  Is this a wrong reference? the initials do not match. How many other mistakes in references? 

Author response:  Action taken, thank you.

 Comments on the Quality of English Language

This manuscript needs to be edited by a professional technical writer. Construction of sentences are not right, the humble "carbon steel" needs to be called but its proper name "carbon steel" or "CS". When you are discussion your material (not something that is in the literature) there are too many other names given to CS, for example "steel metallic" "steel" "steel electrodes",  "steel surfaces", "iron metal", "metallic bulk", etc. 

Author response:  Action taken, thank you dear reviewer for your comments.

Round 2

Reviewer 3 Report

Thank you for addressing the comments from the reviewers. 

It still needs some proofreading. But the world seems to go too fast for anyone to re-read what they originally wrote. Most people do not know what is actually in the page. The best advice is to wait at least two nights since finishing the work. Then print the manuscript and read it again on paper with a pen at hand to be sure that it actually contains what you think you wrote.