A Comparative Study of Chloride Adsorption Ability and Corrosion Protection Effect in Epoxy Coatings of Various Layered Double Hydroxides

Round 1

Reviewer 1 Report

The paper presents an interesting approach based on the A Comparative Study of Chloride Adsorption Ability and Corrosion Protection Effect in Epoxy Coatings of Various Layered Double Hydroxides. However, the innovation of the current research work should be further highlighted and emphasized. At the same time, the authors should consider the following comments to greatly improve the quality of the paper.

1. In the abstract, add a final statement that highlights the importance of this research and its possible potentials. Also, introduce the problem in the initial lines of the abstract.

2. The introduction needs to be improved by relating to the mechanics of the studied materials and their mechanical characteristics. The references to be included are: 10.1177/0021998318790093, 10.1016/j.polymertesting.2017.09.009, 10.1016/j.compstruct.2021.114698, 10.1016/j.jiec.2022.06.023, 10.1002/app.46770, 10.1016/j.porgcoat.2022.107015.

3. Kindly add a table that describes the main physical and chemical properties of the raw materials used in this study.

4. Were the preparation methods described by the authors come in accordance with a certain standard or do they follow previous procedures?

5. The authors mentioned that the coating thickness was kept between 100 to 120 microns. How could the thickness be controlled in that range? Kindly explain it in the coating preparation section.

6. In the Coating morphology and roughness characterization section, what were the SEM operating parameters (accelerating voltage and working depth?) and what was the type of roughness being measured? Kindly sketch the geometry of the samples being tested for roughness. Also, mention the number of times the test was repeated.

7. The conclusion needs to be modified to summarize the research outcomes in short statements with clear observations.

Author Response

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Reviewer 2 Report

This paper describes several synthesizing parameters on the chloride adsorption ability, including different divalent cations, divalent to trivalent cat-ion ratios and hydrothermal time. The work is suitable for publication in MDPI journal but need some changes before acceptance. The following few things needs to be addresses in the revised manuscript.

A. The term emphatically was used in abstract which needs to be replaced with more suitable word. Also, there is sentence “It is well known that the final objective of LDHs used in coatings is to improve the corrosion protection property of the coatings in an optimized way, therefore, the corrosion protection property of the organic coatings with the addition of various LDHs was investigated emphatically in this work by a combination of electrochemical impedance spectroscopy (EIS) and salt spray test” what is the scientific gap or research gap? If something is well known than why research was carried out? If authors want to say something else, please revise the sentence otherwise it is having issue with direction of this paper.

1. Magnification and Micron bar should be same in all SEM images for better comparison (Fig. 2).

2. In the manuscript, with the help of XRD pattern the crystallinity has been described as either high or low crystallinity. It is not scientific way to indicate the crystallinity. There should be a quantitative way to describe the proper values of crystallinity, please add up in your manuscript and also discuss what factors influence the crystallanity in your synthesized samples.

3. Figure 4. Indicate the XRD results of Ca2Al1-LDH, Zn2Al1-LDH and Mg2Al1-LDH. Why Ag2Al1-LDH sample peaks showing the peak broadening phenomena after doping of Mg?

4. None of the EIS diagram showing the Fitting curves, and all fitting parameters should be mentioned properly in a table for easy and quick comparison of coating materials.

5. EIS Phase plot showing one time constant than why two times constant Electrical Equivalent Circuit (EEC) selected for determining the EIS parameters? Please refer the attached papers for correction in the EIS result. https://doi.org/10.1016/j.jmst.2020.11.046   and https://doi.org/10.1016/j.corsci.2021.109693

6. EIS data does not address the Hydroxide layer information (double Hydroxide as mentioned in the title) that needs to be incorporated.

Author Response

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Reviewer 3 Report

The article is interesting, but needs improvement:

1. Abstract

I recommend redoing the abstract, beginning with the part: "It is well known that the final objective of LDHs used in coatings is to improve the corrosion protection property of the coatings in an optimized way, therefore, the corrosion protection property of the organic coatings with the addition of various LDHs was investigated emphatically in this work by a combination of electrochemical impedance spectroscopy (EIS) and salt spray test.It was surprisingly found that although ZnAl-LDH presented a superior chloride adsorption ability in comparison with other LDH samples, CaAl-LDH demonstrated a significantly better corrosion protection. The underlying reasons can be probably attributed to the higher physical barrier effect of CaAl-LDH with typically hexagonal and plate-like morphology due to good compatibility with the epoxy coatings". It is possible to express this part differently, for example: "The corrosion-electrochemical behavior was investigated using electrochemical impedance spectroscopy (EIS) and exposure of samples in a salt spray chamber. It was found that CaAl-LDH showed good corrosion protection due to the higher physical barrier effect of CaAl-LDH with typically hexagonal and plate-like morphology due to good compatibility with the epoxy coatings".

2. Conclusions

You need to summarize your research more clearly and in more detail. The conclusions need to be redone.

3. Discussions

A new Discussion section needs to be added.  In this section you will develop the thought that is now written in the conclusions.

4. Introduction

I recommend at the end of the introduction to write clearly the purpose of the research.  That is, it is necessary to redo the final part of the introduction: " This work emphatically explores the contribution of chloride adsorption on the corrosion protection ability when no inhibitors are intercalated. In this work, the influence of different preparation parameters on the chloride adsorption ability of LDHs was investigated and various LDHs were added in the epoxy coating, the relationship between the chloride adsorption ability and the final obtained corrosion protection ability was firstly evaluated in a practical system. Most importantly, the corrosion protection mechanism of LDHs sample in coatings was further explored and analyzed in this manuscript, which is enlightening and inspiring for clarifying the corrosion mechanism of LDHs in coatings and may provide instructive information for the industrial application of LDHs in the near future".

5. Experimental part

- Sections 2.2.1, 2.2.2, 2.5. It is necessary to add a reference to this methodology, if you can.

- Section 2.2.3. It is worth writing about why 6, 15 and 24 h of the hydrothermal treatment times were chosen.

- Section 2.6. It is necessary to write in which electrons the filming was carried out and at what accelerating voltage. And also write about the EDS methodology. In addition, it is necessary to prescribe the method of determining the roughness. 

- Section 2.7.2. It is necessary to specify the model of the salt spray chamber, as well as the duration of exposure of samples (which systems were tested) in it.

6. Figures

- Pay attention to the authors that the Manuscript must first mention the figure, and the figure itself appears in the text after the first mention of the figure. Please make changes for all figures.

- Figures 9, 10. It is necessary to improve the quality and readability of this figures.

- Figure 19. It is necessary to improve the quality of this figure and highlight in the photos the places that need to be paid attention.

7. References

Authors need to add in more references. Twenty-seven references for such a topic is not very many. Also, the authors in the methodology refer to ISO and other normative documents, but at the same time, these references are missing from the list of references. In addition, the references must be made in accordance with the requirements of the template of this journal. Please make changes accordingly.

8. Typos, word confusions, and other errors

Pay attention to the authors that the Manuscript has word amalgamations, differently written mathematical signs, and other errors that need to be corrected. For example: 200mL, Mg(NO₃)₂·6H₂O and 75*150*2 (differently written multiplication sign),  deionized water.6101 epoxy resin, 24h, 6h and 15h, 40kV, 5.7cm and other word fusions. Please check your Manuscript again, and make changes where necessary (add spaces).

Author Response

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Author Response File: Author Response.docx

Reviewer 4 Report

1) The abstract needs to modify: the abstract should contain Objectives, Methods/Analysis, Findings, and Novelty /Improvement.
2) More explanation is needed for where there is a research gap and what the research goals are. The research gap and the purposes of the research are not explained in detail which leads to the reader missing the significance of the research.
3) However, the manuscript, in its present form, contains several weaknesses. Appropriate revisions to the following points should be undertaken to justify the recommendation for publication.
4) Please add a sentence or two to recap how your study differs from what has already been done in literature to ascertain the contributions more strongly

5) Some assumptions are stated in various sections. Justifications should be provided for these assumptions. Evaluation of how they will affect the results should be made.
6) This raises some concerns regarding the potential overlap with the authors' previous works. The authors should explicitly state the novel contribution of this work, and the similarities and differences of this work with their previous publications.

Author Response

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Round 2

Reviewer 3 Report

I recommend checking the text for errors and typos. Overall, the authors have made significant changes to the Manuscript, the article looks much clearer and more interesting. Thank you!

Author Response

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Reviewer 4 Report

Thanks a lot for all the answers. I accept them. At this point, the article is properly prepared in terms of content and editorial. Thank you very much for the opportunity to review such a good work. At the moment, he accepts the article for further proceedings in the journal.

Author Response

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