Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

coatings-2660608

In this manuscript, the authors provide a comprehensive study regarding “Effect of Zinc Content on Powder Characteristics, Porosity, Microstructure, and Corrosion Behaviour of SLM-Printed Mg-xZn-0.2Mn Alloys for Biomedical Applications”. It is eye-catching and exciting to a researcher in this field. However, some corrections and explanations could be made prior to publishing the paper in the Coatings. Some of my comments and questions on this manuscript are as follows:

1. The abstract should start with the most significant subject of the paper. The reader should understand the main topic of the paper from the first sentence.
2. The author could state whether the porosity percentage or density of the SLMed Mg alloy sample affects the surface quality of the SLMed sample.
3. The author only presents SEM images of the Mg-xZn-0.2Mn alloy samples, but the EDX analysis was not observed. 
4. According to the Mg-Zn binary diagram, after the addition of 7wt.% Zn into Mg-xZn-0.2Mn alloys, the secondary phase was expected to form. While, according to the XRD analysis, no secondary phase was detected.
5. More information regarding the Zinc contents (1wt.% and 7wt.%) in Mg-xZn-0.2Mn must be given. You should clarify the main reason for choosing the range of Zn amount optimal one. Furthermore, further information regarding the constant concentration of Mn should be presented. 
6. The ImageJ-processed images for pore analysis indicate pores by black; however, ImageJ-processed images showed more than the presented value in Fig. 4, for example, Fig. 4C2. 
7. The corrosion process illustration for SLM-printed Mg-xZn-0.2Mn in Hanks’ solution should be updated, and the way Ca-P precipitation on the alloy surface should be clarified.
8. The quality of Fig. 11 should be improved. The kind of corrosion of products and its effect on the corrosion behavior of SLMed Mg alloy should be further highlighted. The author could present the EDX pattern with wt.% and at.% of each element of the white corrosion products to determine the type of Ca-P compounds.
9. The relationship of structural change, including secondary phase and corrosion behavior, should be further highlighted.
10. A reference about the Mg-based alloys may be helpful for this article: Corrosion Science 64 (2012) 184-197. In addition, there are surprisingly small references to the Coatings in the literature despite the extensive relevant literature there. This should be improved. There are several essential papers in recent literature.

Author Response

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Reviewer 2 Report

Comments and Suggestions for Authors

The topics of the work are very interesting and timely. After analyzing the work, the following comments and suggestions come to my mind:

Line 68 - 69 "The present study aims at combining the second and third strategies to reduce the degradation rate of Mg alloys in orthopaedic applications. I believe that the study in the paper was conducted to investigate the effect of the chemical composition and not the printing parameters. The influence of parameters is only described in section 2.2. and 3.2.1.

For some of the studies, there is no information on the population of samples used for each study and the number of measurements taken.

Were potentiodynamic tests performed within +/- 200 mV of OCP?

The area of the samples should be recorded as 0.85x0.85 cm, not 0.85x0.85 cm2.

I believe that item 3 Results and Discussions contains too many subsections that do not relate to the results of the tests performed in the paper (3.2.1, 3.2.2, 3.4). I suggest moving them after modification to the introduction or using them in the discussion of the results obtained. Similar in nature is subsection 3.7 however, the information contained therein is used later in the article.

Figure 10 I propose to supplement with photos of samples in the initial state, this will facilitate the analysis of samples after exposure to Hank's solution.

For some of the results, there is no information about the uncertainties of the obtained results.

Author Response

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Reviewer 3 Report

Comments and Suggestions for Authors

Manuscript presented excellent results with good discussion and my comments are following:

1. Obtained results not well expained in abstarct section, my suggestion for authors to re-write this part.

2. Fig. 7, very low quality also there image (a) but no other images. Please check and revise this figure. 

Author Response

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Author Response File: Author Response.pdf