Review Reports - Crystal Structure and Properties of Zinc Phosphate Layers on Aluminum and Steel Alloy Surfaces

Round 1

Reviewer 1 Report

Comments of crystals-2218833

The main weaknesses of the manuscript:

1. There is no research on the adhesion and thickness of the coating in the article, so this part of the research is added.

2. The discussion points for SEM images are not well supported with other literature findings. It is important to support one's design of study/variable under consideration in citing other relevant work too.

3. The XRD diagram cannot be seen clearly.

4. It is suggested that the conclusion should be expressed more clearly and methodically.

Author Response

Response to comments of Reviewer 1

We thank the Referee for the helpful comments and suggestions.

Comment 1: There is no research on the adhesion and thickness of the coating in the article, so this part of the research is added.

Response: The suggested research on the adhesion of the coating has been performed by a modified scratch-test with an Anton Paar TRB3 type tribometer. This research has been added to the manuscript. The research of the thickness of the coating was given in lines 424-429, the sample were measured by destructive testing, in the course of cross-sectional SEM examinations. The SEM images of the measurements were not included in the article due to lack of space. As an example, the SEM image of the cross-sectional grindings of the AL2-N sample is presented with the measured thickness of the coating:

Please see the attachment

Comment 2: The discussion points for SEM images are not well supported with other literature findings. It is important to support one's design of study/variable under consideration in citing other relevant work too.

Response: The discussion points of SEM images have been completed with the comparison of other literature findings.

Comment 3: The XRD diagram cannot be seen clearly.

Response: The XRD diagram has been replaced to improve its visibility.

Comment 4: It is suggested that the conclusion should be expressed more clearly and methodically.

Response: The conclusion has been changed to make it clearer and more methodically expressed.

Author Response File: Author Response.docx

Reviewer 2 Report

The article concerns the production of phosphate coating using nitrite and nitroguanidine accelerators on aluminum and steel alloys.

Notes to the article:

Introduction

Line 45-62: The authors list the types of materials used for vehicle structural components such as aluminum and alloy steels. They also indicate that "Zinc phosphate coatings on metal surfaces are the first layer of multi-layer corrosion protection coating". Currently, the car body is commonly made of sheets with hot dip galvanizing coatings (galvannealing coatings). And this is the first coating of the anti-corrosion system. In addition, the phosphate coating is to ensure good adhesion to hot dip galvanizing coatings, as problems with paint adhesion to zinc coatings are commonly known. In my opinion, this is important information about the application of the subject of research, which the authors omit in the Introduction.

In the Introduction, the authors state several times that aluminum is used for structural elements. My question: is it about "pure" aluminum or some alloys of this metal? Because aluminum, like most other metals, is marginally used in its "pure" form.

Lines 75-118: I find the description of the phosphating process in the Introduction redundant. Rather, this information should be used in the discussion and interpretation of research results.

Introduction describes used accelerators such as nitrite and nitroguanidine. The article presents the results of research with such accelerators. The introduction lacks justification, giving reasons for undertaking such research. I believe that the introduction should be supplemented with information why the research presented in the article is important.

Materials and Methods

The materials, methods and preparation of the coatings have been sufficiently described

Results and Discussion

Chapter 3 presents and describes the test results. However, I believe that the discussion of the results is at an insufficient level. There is no proper discussion of research results in relation to the existing state of knowledge. There is no comparison with alternative solutions. There is also no scientific interpretation of the research results or, for example, a scientific explanation of the phenomena occurring during the constitution of coatings.

The interpretation presented in lines 490-507 is unclear and does not result from the presented test results. These are rather recommendations for the conduct of the technological process.

This approach to research results makes the article look like a research report, not a scientific article.

Other notes on Chapter 3:

Fig.6: SEM images at 5 µm scale are illegible.

Table 4: The area from which the EDX analysis was performed should be shown (marked) on the microstructure images. In addition, the quantification of oxygen by EDX is uncertain and may be subject to significant error.

Chapter 3.2: A chapter should not start with a drawing.

Fig. 8 XRD spectra are unreadable

References

I also have reservations about References. The subject of the article is interesting for automotive and phosphate coatings are widely used there. Therefore, I am surprised that the authors refer to the latest literature, e.g. from the last 10 years, only 4 times (2020, 2018, 2015, 2013). I think the authors should study the literature better.

In general opinion, the content of the article is interesting and can be of great utilitarian importance, therefore I believe that the article needs improvement and a more scientific interpretation of the research results.

Author Response

We thank the Referee for the valuable remarks and notes.

Comment 1: Introduction

Response: According to the Reviewer's proposal, the Introduction has been completed with the information related to hot dip galvanizing coatings.

Comment 2: In the Introduction, the authors state several times that aluminum is used for structural elements. My question: is it about "pure" aluminum or some alloys of this metal? Because aluminum, like most other metals, is marginally used in its "pure" form.

Response: Of course, it is about aluminum alloy. We have corrected this mistake in the text.

Comment 3: Lines 75-118: I find the description of the phosphating process in the Introduction redundant. Rather, this information should be used in the discussion and interpretation of research results.

Response: The description of the phosphating process has been shortened. The discussion has been modified accordingly.

Comment 4: Introduction describes used accelerators such as nitrite and nitroguanidine. The article presents the results of research with such accelerators. The introduction lacks justification, giving reasons for undertaking such research. I believe that the introduction should be supplemented with information why the research presented in the article is important.

Response: The introduction has been supplemented with the required information.

Comment 5: Materials and Methods

The materials, methods and preparation of the coatings have been sufficiently described.

Response: Thank you for this positive comment.

Comment 6: Results and Discussion

Response: The Results and Discussion has been completed according to the Reviewer's suggestion. We have tried to discuss the research results in relation to the literature and to give the scientific explanation of the occurred phenomena. We hope that the Results and Discussion part will be acceptable in its present form.

Comment 7: The interpretation presented in lines 490-507 is unclear and does not result from the presented test results. These are rather recommendations for the conduct of the technological process. This approach to research results makes the article look like a research report, not a scientific article.

Response: The mentioned interpretation has been modified to clear up the findings.

Comment 8: Other notes on Chapter 3: Fig.6: SEM images at 5 µm scale are illegible.

Response: These SEM images have been improved.

Comment 9: Table 4: The area from which the EDX analysis was performed should be shown (marked) on the microstructure images. In addition, the quantification of oxygen by EDX is uncertain and may be subject to significant error.

Response: The points of the EDX spot analysis (Table 4) have been marked clearly in Figure 6. The data have been changed in Table 4, now they are presented without the oxygen content.

Comment 10: Chapter 3.2: A chapter should not start with a drawing.

Response: The drawing (Figure 8) has been shifted. Chapter 3.2 now starts with text.

Comment 11: Fig. 8 XRD spectra are unreadable.

Response: The quality of Figure 8 has been improved.

Comment 12: References

I also have reservations about References. The subject of the article is interesting for automotive and phosphate coatings are widely used there. Therefore, I am surprised that the authors refer to the latest literature, e.g., from the last 10 years, only 4 times (2020, 2018, 2015, 2013). I think the authors should study the literature better.

Response: We have added references from the last 10 years as suggested by the reviewer.

Comment 13: In general opinion, the content of the article is interesting and can be of great utilitarian importance, therefore I believe that the article needs improvement and a more scientific interpretation of the research results.

Response: We thank the Reviewer for the important comments and suggestions. We have revised our paper accordingly and feel that the Reviewer's comments have helped to improve the quality of the paper.

Reviewer 3 Report

The presented article is devoted to the study of crystal structure and properties of zinc phosphate layers on aluminum and steel surfaces and represents a certain interest to the specialists in this field. The abstract corresponds to the main content of the article. All the methods used in the work are carefully described. These methods are modern, reasonable, accurate and widely used in the research practice. The main key results obtained in the work are listed in the conclusion. The work can be accepted for publication after the revisions.

There are several non-existent remarks to the work.

1) The novelty of this work is not obvious. It is necessary to improve the introduction and justify the research carried out in this work.

2) The images of the cross-sectional grindings shown in Figure 6 need to be improved. On these images, you can see several points located in different parts of the section. Please specify to which points of the cross section of the polished samples the point elemental analysis (Table 4) was applied.

3) The illustration of X-ray diffraction patterns of phosphate coatings needs to be improved.

Author Response

We thank the Referee for the constructive remarks and suggestions.

Comment 1: The presented article is devoted to the study of crystal structure and properties of zinc phosphate layers on aluminum and steel surfaces and represents a certain interest to the specialists in this field. The abstract corresponds to the main content of the article. All the methods used in the work are carefully described. These methods are modern, reasonable, accurate and widely used in the research practice. The main key results obtained in the work are listed in the conclusion. The work can be accepted for publication after the revisions.

Response: We have revised our article in line with the Reviewer's comments and hope that the revised version will be acceptable. I would like to answer your comments point by point.

Comment 2: There are several non-existent remarks to the work.

The novelty of this work is not obvious. It is necessary to improve the introduction and justify the research carried out in this work.

Response: The introduction has been improved and the novelty of this work has been emphasized.

Comment 3: The images of the cross-sectional grindings shown in Figure 6 need to be improved. On these images, you can see several points located in different parts of the section. Please specify to which points of the cross section of the polished samples the point elemental analysis (Table 4) was applied.

Response: The images of the cross-sectional grindings have been improved. The points of the EDX spot analysis (Table 4) have been specified in Figure 6.

Comment 4: The illustration of X-ray diffraction patterns of phosphate coatings needs to be improved.

Response: The illustrations of X-ray diffraction patterns (in Figure 8) have been improved.

Round 2

Reviewer 1 Report

Comments of crystals-2218833

The manuscript is well revised and can be published in present form.

Comments for author File: Comments.docx

Reviewer 2 Report

The authors corrected the Introduction. They supplemented the research results and improved their discussion by increasing the scientific quality. They also supplemented references referring to literature from recent years.

I believe that the article meets the minimum scientific level for publication.