Corrosion Mechanisms of a Biodegradable Zn-0.4Li Alloy in Simulated Gastrointestinal Environment

Round 1

Reviewer 1 Report

This submission cannot be accepted in its current form but can readily be made acceptable by addressing the following issues.

1. The authors must define how alloy composition is specified here. Is the Li content given in atom percent or weight percent (or atom fraction or weight fraction)? Given the large difference in atomic weight of Li and Zn it matters greatly what measure of composition is being used. If the Li content is given in atom percentage the LiZn4 compound would likely form by precipitation from a solid solution on cooling whereas this compound would form during eutectic decomposition if weight percentage were used.

2. The microscopy in Figure 1 is insufficient to address the issue raised in comment 1. The authors should review their microscopy results as they consider the issue raised in comment 1 and see if they have results that support the measure of composition used in this research.

Author Response

We appreciate your judgment and helpful comments of my manuscript. Those comments are all valuable and helpful for revising and improving our paper. We thoroughly considered each comment and made thoughtful corrections to the paper. Those comments are all valuable and helpful for revising and improving our paper. The changes in the revised manuscript are highlighted in red. The paper's principal corrections and responses to the reviewers' criticisms are shown in the attachment.

Please see the attachment.

Author Response File: Author Response.doc

Reviewer 2 Report

I have reviewed the manuscript coatings-2150383 entitled "Corrosion Mechanisms of a Biodegradable Zn-0.4Li Alloy in Simulated Gastrointestinal Environment" for publication in the Coatings journal. The results are interesting. However, some parts of the manuscript should be improved before it is considered to be acceptable. In my opinion, the following points have to be considered:

1. Add implications of this study at the end of the abstract. Please also revise the typo error "Li+" and "Zn2+". 

2. The scientific novelty in this paper should be shown more clearly in the introduction part.

3. On page 1, line 36, the sentence “Studies on Zn alloys have achieved progress in various areas, such as vascular stents and orthopaedics” also needs the following reference: https://doi.org/10.1016/j.corsci.2020.108781

4. The experimental section is poorly written. In this section, more detailed information should be provided. For example, the purity and manufacturer of reagents should be given.

5. The authors claimed that electrochemical measurements were conducted three times, but the EIS results in Tables 2 and 3 have been reported without error reports.   

6. Please provide a proper reference for equation (1).

7. It is necessary to add in the text information related to the health problems associated with the Zn and Li overdose. It is necessary to present such information since a person receiving an implant of this material may have health problems related to titanium overdose.

8. How did the author calculate the corrosion rate? How did the author find Ecorr and Icorr values? For Tafel extrapolation, both anodic and cathodic sides of the curves were considered, or only the cathodic side? The curves shown in the anodic branches also reveal that the anodic curve cannot be fitted to the Tafel equation, since no well-defined peaks can be noted, indicating that more than one phase is corroding. Thus, two Tafel slopes can be obtained from anodic curves. Finally, I recommend that the authors reed the Mccafferty paper “Corrosion Science 47.12 (2005): 3202-3215” in order to help him to present a full revision of the discussions related to the data displayed in Fig. 6b. It is mandatory that this is described critically.

9. It is necessary to add some characteristic frequencies to the Nyquist diagrams.

10. In the manuscript, the authors sometimes use x/y, and sometimes x.y-1, and also sometimes x y-1 and xy-1, please check and choose the unified unit for the values. For example please see section 2.2.

11. The English of the whole paper is good, but some errors could still be found. Therefore, the English of the paper should be reviewed.

12. The quality of all figures needs to be improved. Please remember that these figures will be shrunk once the paper is published and no one can read anything as a result. 

13. There are some formatting mistakes in the references section, I suggest the authors check and correct them. For example, there are incomplete references or with erroneous data, others with typos in the journal name or chemical formulae in the title.

Author Response

We appreciate your judgment and helpful comments of my manuscript. Those comments are all valuable and helpful for revising and improving our paper. We thoroughly considered each comment and made thoughtful corrections to the paper. Those comments are all valuable and helpful for revising and improving our paper. The changes in the revised manuscript are highlighted in red. The paper's principal corrections and responses to the reviewers' criticisms flow as follows:

Please refer to the attachment.

Author Response File: Author Response.doc

Reviewer 3 Report

Comments for author File: Comments.docx

Author Response

We appreciate your judgment and helpful comments of my manuscript. Those comments are all valuable and helpful for revising and improving our paper. We thoroughly considered each comment and made thoughtful corrections to the paper. Those comments are all valuable and helpful for revising and improving our paper. The changes in the revised manuscript are highlighted in red. The paper's principal corrections and responses to the reviewers' criticisms flow as follows:

Please refer to the attachment.

Author Response File: Author Response.doc

Reviewer 4 Report

Corrosion Mechanisms of a Biodegradable Zn-0.4Li Alloy in Simulated Gastrointestinal Environment

Comments to authors

1.     Include the significance of Li and demonstrate the novelty of the work in Introduction session.

2.     Mention the measured potential range used in PDP with respect to OCP in session 2.4.

3.     How the authors confirm the presence of eutectic and lamellar phases in Figure 1 of the manuscript without EDS mapping.

4.     Check the XRD plot (Figure 3c, d), some of the plot is not fitted.

5.     OCP value of SIF is not stabilize within the test period. How the author suggests it?

6.     Why the Li 1s and P 2p are not listed in the table 1 of the article?

7.     The conclusion of the article only shows the significance/observations from immersion test. It recommended to include the results of electrochemical test and also made comparison and report the feasible method to predict the corrosion rate.

 

8.     It is recommended to rewrite the abstract of the article. 

 

Author Response

We appreciate your judgment and helpful comments of my manuscript. Those comments are all valuable and helpful for revising and improving our paper. We thoroughly considered each comment and made thoughtful corrections to the paper. Those comments are all valuable and helpful for revising and improving our paper. The changes in the revised manuscript are highlighted in red. The paper's principal corrections and responses to the reviewers' criticisms flow as follows:

Please refer to the attachment.

Author Response File: Author Response.doc

Round 2

Reviewer 1 Report

It would be helpful to readers to use one measure of composition, i.e., wt.pct. Li and use it consistently throughout the manuscript and every time composition is mentioned in the text and figure captions. It is distracting for a given compositioin to be stated in wt. pct. sometimes and without specification in other places.

Reviewer 2 Report

I have reviewed the re-submission and the authors have carefully amended their manuscript following the additional reviewers' suggestions.