In Situ Synthesis of Graphene Oxide-Sealed LDHs Coatings: A Novel Approach to Enhancing Corrosion Resistance and Tribological Performance on Magnesium Alloys

Round 1

Reviewer 1 Report

The submitted article is devoted to the synthesis and study of graphene oxide-sealed LDHs coatings on magnesium alloys and is of interest to specialists in this field. The authors describe a new simple approach to the synthesis of such coatings, but the results of corrosion tests are not impressive.

I cannot recommend this article for publication as presented, as it has many weak points.

 1. The E_corr of the LDHs/GO coating is -1.524 VSCE, which is only 0.097 VSCE more than the E_corr of the magnesium alloy substrate. This is a very small shift in the corrosion potential and may be within the measurement error. Corrosion tests should be repeated at least three times to check the reproducibility of the results.

2. Page 7, line 3 from bottom. How did you determine the corrosion currents? Judging by the polarization curves, they are somewhat larger than those presented in the text. Please explain why the corrosion currents are negative. Such a small change in corrosion currents also does not indicate an improvement in the corrosion resistance of the samples.

3. Page 5, line 7 from top. Explain the mechanism of the catalytic action of GO in the growth of LDHs crystals.

4. Page 8, line 13 from top. How can the NO₃^- in the LDHs layer scavenge Cl^-?

5. Figure 6. The signature is not correct. The figure shows the results of elemental energy dispersive analysis, not the energy spectrum of LDHs and LDHs/GO coatings. Pictures should be improved, font size should be increased.

6. Please describe in more detail in the experimental section the electrochemical measurements made using electrochemical impedance spectroscopy and potentiodynamic polarization (frequency range, amplitude and scan rate, scan range).

7. The Figure 6 need to be improved.

Therefore, in my opinion, the manuscript requires a major revision according to the comments before acceptance.

   
Some sentences are hard to read and need to be improved.
 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Whether author measured surface roughness?

On what basis 2N load for friction test is considered?

How author ensured exact contact between surfaces in friction tester for that low load?

Fig.3, encircle your findings

Why time was restricted to 16 min in friction test?

Whether dry case is considered or lubricant is used?

Conclusion is very general

 

Minor editing of English language required

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Round 2

Reviewer 1 Report

The authors took into account most of the reviewers' comments and revised the manuscript accordingly. However, a few remarks remain on the work.

1. Corrosion current is determined from the abscissa of the polarization curve, which shows the logarithms of the current density. The logarithms of negative numbers are not defined in real numbers, so corrosion current densities cannot be obtained with a minus sign. See references [14], [28], https://www.sciencedirect.com/science/article/pii/S2213956720300566 and many others to ensure that it is correct to write 6.117 μA/cm2 and not -6.117 μA/cm2.

 2. Page 8, line 13 from top.

Indeed, LDHs have strengths as anion scavengers. he NO^-₃ ion in the LDHs layer can be exchanged for Cl^- ion from aggressive environments, but not scavenge it. I think that the expression "the NO₃^- in the LDHs layer can scavenge Cl^-" is not entirely correct.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Round 3

Reviewer 1 Report

The authors have addressed the comments  and revised the manuscript accordingly.  I recommend accepting the manuscript.