Effect of Microstructure on Layered Double Hydroxides Film Growth on Mg-2Zn-xMn Alloy
Round 1
Reviewer 1 Report
The submitted manuscript entitled “Effect of microstructure on layered double hydroxides film growth on Mg-2Zn-xMn alloy” has some interesting results. But I have several minor concerns which should be addressed before publication:
Line 89 is written "... Figure S1 ..." - there is no such Figure in the manuscript.
Line 97 The authors in the table description wrote "The weight percentage of metallic powders for preparation of Mg-2Zn-xMn alloy" and in the table they give the value in at. % - please standardize it.
Line 175 is written "… in Figs. S2 over S3… ”- there is no such Figures in the manuscript.
Line 250 - 252 - references number 4 and 5 is the same reference, so please correct the numbering of all references and include these corrections in the manuscript.
Question
In chapter 3.1, the authors in lines 89 to 96 carry out an analysis of structure components from the literature and should use X-ray diffraction for this purpose, especially since they used this technique to research the LDHs film on Mg alloys. Why didn't they do it?
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Dear Authors,
Thank you for interesting article, which topic concerns the preparation of layered double hydroxides coating, which allowe the effective corrosion protection for Mg alloys. In reviewed manuscript, the necessity to determine the effect of the alloy microstructure on the studied coatings growth and improving the corrosion resistance of Mg alloys.
The article requires the following amendments:
Materials and Methods: lines 68-77;
There is no information on the prepare method of samples for the metallographic measurements? What apparatus was used?
The measurement conditions used in individual analytical methods should be given.
Results:
3.2. Surface morphology............
Information about the roughness and porosity of the produced LDHs coatings should be added.
Have the mechanical properties of the produced films been studied?
The scratch test results would be especially important and also the determination the possible delamination.
3.3. lines 131-133 and Figure 5(b)...
In my opinion, assigning the stretching vibrations to the -OH groups and water molecules should be the opposite, i.e. the wide band at 3460 cm-1 should be attributed to asymetric and symmetric stretching vibrations of water molecules, while the sharp band at 3693 cm-1 should be attributed to stretchnig vibrations of -OH groups. The complex shape of the H-O-H bending vibrations band (c.a. 1640 cm-1) suggests a differences in water particle interaction in this system.
In my opinion, the reviewed manuscript may be acepted to publication in COATINGS after minor revision.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Manuscript present interesting study of hydroxide films deposited onto Mn alloy substrates of different composition. Before go ahead authors must makes the following corrections:
- Authors wrote that in Figure 2(a)) an average grain size is about 20 μm. How tis values was obtained. Also, from figure visually comparing grins with given scale it looks quite smaller. Can author comment on it?
- Discussing results of figure 2 authors compare them with results of ref. [10], but nothing is said what kind of experiment was done and presented in ref. [10]. And, what is consistent with the reported result [10], what increasing Mn content, the alloy microstructure is gradually refined? Autos must give more detail explanation. The same about results of figure 3 which are compared with ref [9].
- Tables 1 and 2 are about the same, composition of samples, only unites differ. Both tables can be easily merged and would be more easily to compare the samples.
- Table 3, the composition O+Mg+Al gives 100%, but there are LDH films, what about hydrogen? Hydroxides without hydrogen? More over, XRD in figure 5 show existence of Mg(OH)2. FTIR spectra also shows existence of hydrogen.
- Legend of figure 3 talks about (a), (b) and (c) pictures. What is in others from (d) to (i)? All pictures must be described. In text results presented in figure results presented in figure are not discussed well, discussion must be extended describing all pictures presented in figure 3.
- What means layers in substrate seen in figure 4 c?
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
The paper presents an important study on the effect of microstructure on layered double hydroxides film growth. Mg2Zn has been alloyed with Mn, resulting in grain refinement (but not fully recrystallized). Corrosion behavior was measured by polarization and hydrogen evaluation from immersion. Optical microcopy, SEM, XRD and FTIR. The discussion is also based on investigations the appearance of the corrosion surface and 3 cross-section of the film on the substrate. The results present valuable information to the field of enhancing the corrosion resistance of Mg-Zn alloys, even the application is not really clear. There are a few suggestions and comments, which could be addressed to improve the quality of the paper:
- please add the aimed application to the introduction
- very important is to check the references: reference 4 goes on to reference 5 – therefore all the following references do not agree
- please do not use abbreviation with the abstract, page 1 line 18: that statement is not correct, there are corrosion products, but maybe not visible by eyes – obvious is that there is no local corrosion
- I would be recommended to add additional literature reference with Mg-2Zn – you have added some with much higher Zn-content
- page 2, line 55: what about the impurities Fe, Cu, Ni? They are important, when investigating corrosion
- page 3: adding Mn refines the microstructure, but makes it more inhomogeneous… your study concentrates on the corrosion behavior, however, are there data on mechanical properties, strength, hardness, ductility… incomplete dynamic recrystallization usually has no positive effect on mech. properties
- page 3, line 89… please comment on Table 1 and 2 or better rather discuss the difference in composition – that is not really clear
- page 4, line 100: Figure 3c also shows local corrosion! May more spots, but you cannot call it “continuous” … also counts for line 105 Fig. 3g
- page 4, line 103: it is highly recommended to add cross-section micrographs of the cracks – also to see, if there are corrosion pits underneath, more cross-section micrographs than already shown in Fig 4 are important to have enough information for Fig. 9!
- page 4, line 106/107: perpendicular? Collapse? Please describe this more clearly
- page 6, line 115: please add a bit of statistics to the value of the thickness of the layer
- Figure 4: is there an effect of the layer thickness on the chemical composition (their distribution?)
- Figures 5, 6, 7 and 8 show a different description of the alloys: what do you not use ZM20, ZM21, ZM22?
- page 8, line 185: please discuss for the Mn-containing alloys why there is a decrease before it steady increases again
- page 8, Figure 9: here come more cross-sectional micrographs to use, Figure 4 does not show the microstructural features… (second phases, un- recrystallized grains …)
- page 9, line 206: here come more cross-sectional micrographs to use, too, are there pits in the alloy underneath the cracks in the layer
- page 10, conclusion, line 221: …protection for the Mg-Zn alloy … and … Among these three alloys…
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Authors made correction according to my suggestions and significantly increased the quality of manuscript
Author Response
Thank you for your contribution to our manuscript. The quality of the article has been greatly improved.
Reviewer 4 Report
Thank you for addressing the comments and suggestions.
One suggestion remains: Impurities Fe, Cu, Ni: they are important, when investigating corrosion
In your answer, you mention that the impurities are very small – however, for quality reason: please add the information – than the knows, that the impurities are not influencing the corrosion behavior
Author Response
Thank you for your valuable comments. We have added information about impurity elements based on your suggestions. Revisions are marked in red in the manuscript. (Lines 56-58 on page 2)
