Micro-Arc Oxidation Phenomenon for Producing Coatings of AZ31B Mg Alloy Using Na3PO4 with Varying KOH Concentrations and Voltages: A Study
Round 1
Reviewer 1 Report
Manuscript ID: coatings-2496165
Title: Micro-arc oxidation phenomenon for producing coatings of AZ31B Mg alloy using Na3PO4 with varying KOH concentrations and voltages: A study
Authors: Han Yan, Yuming Qi, Xuejun Cui *, Chunyang Li
Comments:
The manuscript reports on the fabrication of protective coatings on the AZ31B MG alloy by micro-arc-oxidation in a solution of Na3PO4 and in a mixture of Na3PO4 and KOH at various component concentrations and voltage. The thickness, roughness, and corrosion resistance of the resulting coating were measured. The authors did not achieve any significant success in improving the quality of the protective coatings of the investigated alloy. The introduction does not allow the reader to understand why exactly Na3PO4 and KOH were chosen as the objects of study.
1. The meaning of the term “single Na3PO4 solution” is not clear. Use "Na3PO4 monosalt solution" instead, for example.
2. Explain in more detail how the porosity of the coating was measured.
3. The photos in tables 4 and 5 do nothing to help the reader understand the results of the study. They should either be discussed in detail in the text or moved to the supporting information section.
4. What is the depth of the surface cavities (called pores in the text) relative to the average thickness of the coating layer?
5. “The development of MAO coatings may be encouraged by the stoichiometry of P.” Explain the meaning of the sentence in more detail.
6. “Even though the MAO coating is thick when using a Na3PO4 solution as the electrolyte, it has a high degree of roughness and only moderate corrosion resistance.” How was the corrosion resistance measured?
7. The photos in tables 8 and 9 do nothing to help the reader understand the results of the study. They should either be discussed in detail in the text or moved to the supporting information section.
8. Line 191: change to Fig. 5
9. Line 205: change to Fig. 6
10. Line 211: change to Fig 7
11. Line 222: change to Fig. 8a
Author Response
Plesase see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Manuscript ID: coatings-2496165 entitled " Micro-arc oxidation phenomenon for producing coatings of 2 AZ31B Mg alloy using Na3PO4 with varying KOH concentrations and voltages: A study"
Comments to the authors
In general, the article is interesting, and the information provided by the authors is important.
After the review of the manuscript, I have the following comments.
1. According to the limits of the journal, the Tables and Figures Must be presented after they are mentioned. Please take it into account.
2. Pag. 2, line 76, says, "Various electrolytes were prepared by dissolving 20, 75 25, 30, 35, and 40 g/L of Na3PO4 with deionized water in a cylinder".
Please indicate what material the cylinder is made of, if possible.
3. Figure 5 is not discussed in the manuscript
4. Figures 6, 7, and 8 do not describe what the authors indicate. Please verify.
5. Line 222, the authors describe Figure 9. However, that Figure does not appear in the manuscript.
6. In my opinion, more discussion of the results is needed.
The results are not compared with the literature, so their validity cannot be recognized.
The results are presented as a report; they lack a bit of scientific discussion.
Comments for author File: 
Comments.pdf
Minor editing of English language required
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
The paper deals with...
1. There is no reference from Coatings cited in the paper as if this topic has not been discussed in the journal previously; please add some.
2. I hardly find the prime novelty of this research - similar works were done almost a decade ago (see for example: 10.1002/sia.5339, 10.1016/j.apsusc.2012.08.099). This is the weakest aspect of the paper.
3. I am not sure as to the structure of the paper, in which all the results are shown together after the main text. It makes the reading very difficult.
4. There is too much data shown in tables - much too much concerning especially those with graphical insets. Apart from that, the images included therein are of poor quality. Tables 4-11 should be definitely re-organized.
5. Remaining notes and comments are included in the enclosed text
Comments for author File: Comments.pdf
No comments, language is fine.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
I have no more comments that would necessitate another review cycle.
Reviewer 3 Report
I have found that all the issues raised in the review have been answered by the authors, hence I have no other questions.
