Electrochemical Corrosion Behavior of Pure Mg Processed by Powder Metallurgy

Round 1

Reviewer 1 Report

Paper is related to an interesting topic, however I recommend a major revision of this manuscript.

1. Why these parameters of compacting were taken into consideration in this work? Especially, the choice of temperature is questionable.
2. Different methods of powder metallurgy should be shortly presented in introduction.
3. In introduction a big part is related to improvement of Mg and Mg-based materials using coatings and alloying. However, in this work neither coating nor alloying is used. I recommend reducing this part significantly and concentrate more on works with more similar topics (for example influence of process parameters). What is about other parameters except pressure or temperature of the process?
4. Why different time of pressing was used (20s at RT and 1h at 400°C)?
5. Various authors found that porosity measurements based on optical micrograph will lead to insufficient quality of porosity measurements. How was porosity measured at the end in this work since two methods were described?
6. In Fig. 2a SEM micrograph is missing and SEM should be presented as a separate Figure in higher quality since it is difficult to recognize any details.
7. Porosity decrease with increasing temperature, but what is about influence of compaction pressure?
8. Page 5 Line 193 "...pore size lower that 10m..."?
9. I printed the pdf version of the manuscript, but figure 3 looks more than strange to me. Authors should present a new version of this figure and in the future please check manuscript carefully before submission, because next time it could be rejected due to this reason.
10. Last part of the manuscript was not reviewed because figure 3 was missing in sufficient quality.

Author Response

1. Why these parameters of compacting were taken into consideration in this work? Especially, the choice of temperature is questionable.

A: The parameters for samples preparation were chosen based on our previous research. We had chosen the samples reaching the best mechanical properties with the lowest porosity when prepared at RT and elevated temperature. The wrought Mg was chosen only to have comparison with a conventional material.

The information was added into the manuscript.

(M. Březina, J. Minda, P. Doležal, M. Krystýnová, S. Fintová, J. Zapletal, J. Wasserbauer and P. Ptáček, "Characterization of Powder Metallurgy Processed Pure Magnesium Materials for Biomedical Applications", Metals, vol. 7, no. 11, pp. 461-, 2017.)

2. Different methods of powder metallurgy should be shortly presented in introduction.

A: The methods were briefly mentioned in the Introduction.

3. In introduction a big part is related to improvement of Mg and Mg-based materials using coatings and alloying. However, in this work neither coating nor alloying is used. I recommend reducing this part significantly and concentrate more on works with more similar topics (for example influence of process parameters). What is about other parameters except pressure or temperature of the process?

A: Whole the introduction was modified and we suppose is more suitable to the topic of the manuscript now.

4. Why different time of pressing was used (20s at RT and 1h at 400°C)?

A: As mentioned in the answer to the first task, we had chosen the parameters based on the previous study. The information was added into the manuscript.

(M. Březina, J. Minda, P. Doležal, M. Krystýnová, S. Fintová, J. Zapletal, J. Wasserbauer and P. Ptáček, "Characterization of Powder Metallurgy Processed Pure Magnesium Materials for Biomedical Applications", Metals, vol. 7, no. 11, pp. 461-, 2017.)

5. Various authors found that porosity measurements based on optical micrograph will lead to insufficient quality of porosity measurements. How was porosity measured at the end in this work since two methods were described?

A: The light optical microscopy was used only for the primary analysis of the porosity and to distinguish its character, however, the exact value was calculated according to the dimensions and mass of the sample and the density of pure Mg. it was clarified in the manuscript.

6. In Fig. 2a SEM micrograph is missing and SEM should be presented as a separate Figure in higher quality since it is difficult to recognize any details.

A: Authors believed the microstructure is obvious on LM micrographs and the SEM were added just to document the interface between powder particles end eventual porosity and oxide layer on particles. The information was added to the manuscript. Actually, we can add the SEM micrographs, however, due to the contrast on SEM figures, the porosity and the particles interface will be not obvious on lower magnification images and adding the high magnification will not provide any additional information.

7. Porosity decrease with increasing temperature, but what is about influence of compaction pressure?

A: In the present study only the pressure of 500 MPa for samples preparation was applied so we did not suppose it is important to mention the influence of the pressure on material porosity in the manuscript. We added the information into the Introduction and briefly also into the Discussion.

8. Page 5 Line 193 "...pore size lower that 10m..."?

A: The wrong unit was corrected into mm.

9. I printed the pdf version of the manuscript, but figure 3 looks more than strange to me. Authors should present a new version of this figure and in the future please check manuscript carefully before submission, because next time it could be rejected due to this reason.

A: Authors would like to apologize for this mistake. It was caused due to the inappropriate format of the document uploaded. Manuscript in word format was replaced now and we hope the figures will be correct.

10. Last part of the manuscript was not reviewed because figure 3 was missing in sufficient quality.

A: Again, we are sorry for the mistake.

Reviewer 2 Report

Dear Authors,

The topic looks interesting and the manuscript prepared well however to match with the Journal criteria and improve the paper for the other readers, please follow the comments:

1) More than 60% of references used in the introduction are older than 2015. Please add more recent findings.

2) Figure 3 is not arranged correctly. Can't see any curve. 

3) Better to present different patterns of corrosion against other parameters in addition to tables.

4) If the authors mapped the chemical components, please provide the graphical results.

5) English should check by a native technical English speaker.

Author Response

1. More than 60% of references used in the introduction are older than 2015. Please add more recent findings.

A: The Introduction was modified and more recent literature resources were added.

2. Figure 3 is not arranged correctly. Can't see any curve. 
3. A: Authors would like to apologize for this mistake. It was caused due to the inappropriate format of the document uploaded. Manuscript in word format was replaced now and we hope the figures will be correct.
4. Better to present different patterns of corrosion against other parameters in addition to tables.

A: We are sorry, but we do not understand what should we add to the manuscript. Can you be more specific please?

5. If the authors mapped the chemical components, please provide the graphical results.

A: Chemical composition(EDS) was performed in the case of Mg powder particles

6. English should check by a native technical English speaker.

A: Actually, before sending the manuscript to the journal, the native speaker from the field corrected it. We asked another member of our department for language checking.

Round 2

Reviewer 1 Report

Paper could be accepted in presented form

Author Response

Thanks for your time and effort.