The Effect of the Methyl and Ethyl Group of the Acrylate Precursor in Hybrid Silane Coatings Used for Corrosion Protection of Aluminium Alloy 7075-T6

Round 1

Reviewer 1 Report

This manuscript describes the preparation and the thorough characterization of two polysiloxane hybrid materials and their application as corrosion protection coatings on aluminum alloy. The topic of the work is relevant, the materials are investigated by appropriate and up-to-date methods, the experiments are very well designed and the results are presented in a convincing way. Accordingly, I believe the manuscript can be accepted for publication after minor stylistic improvements.

My only question is whether the authors experienced radiation-induced degradation of the polymer coating during the XPS experiment.

My recommendations for improvement are as follows:

line 122: term "another" seems to be unsuitable here; maybe "The appropriate" looks better. line 179: please specify the source of the atomic sensitivity factors line 190: I guess electron gun was used to prevent charging line 216: affected area should be more, not less line 276: "stretching " seems to be the appropriate term instead of "starching" line 287: is term "TEOS" necessary? Fig. 2: maybe indication of the ethoxy-related peaks as described in lines 322-323 could be useful lines 331, 334: I would recommend to avoid repeating exactly the same numbers for the two layers: "...three peaks appear for both siloxane-PMMA and siloxane-PEMA at..." may look better Fig. 3, 4: I believe the two figures could be united: the fitting components could easily be shown in Fig. 3.

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Reviewer’s report on MS #Coatings-709302

“The Effect of the Methyl and Ethyl Group of the Acrylate Precursor in Hybrid Silane Coatings Used for Corrosion Protection of Aluminium Alloy 7075-T6”

 

This manuscript reports a comparative study on polysiloxane hybrid sol-gel coatings obtained on the surface of the alloy AA7075-T5. The topic of the study suits the scope of the journal Coatings and can be of interest to a potential reader. However, I have some comments and suggestions that need to be addressed before it can be accepted for publication. The manuscript also has some grammar mistakes. A careful check must be done.

Below are listed my comments and suggestions to consider, which may improve the scientific level and readability of paper:

Line 16, 59–60, 113, 128, 129. No space is needed in 3-(trimethoxysilyl) propyl, (3-glycidyloxypropyl) trimethoxysilane, poly (methyl…), (poly (ethyl…). Line 19, 129. Use either maptms or MAPTMS as an abbreviation. Line 21. Please provide the concentration of NaCl solution. More specific details must be added to Abstract. Please focus more on the results than the methods used. It is important in order to make the potential reader aware of the achievements of the paper, not experimental part. Maybe consider adding your silane to Keywords. Please check the order of the words in lines 41–42. Lines 45–47. In principle, IGC is usually of galvanic nature in Al alloys as a grain boundary, in this case, acts as an anode. Two types you mentioned belong to different classifications and thus it would be better to write “… in particular to localized galvanic processes…”.

I have also comment on the part “that take place between the various intermetallic particles added to the aluminium matrix”. Local galvanic effects are more typical to occur between intermetallic particles (IMPs) and Al matrix as IMPs are dispersed in the matrix (the most common case). Please explain if you mean some special IMP-IMP interactions. Moreover, IMPs are formed in the Al alloy during heat treatment, not added to it as an independent phase before extrusion/cast. I suggest rewriting this part of the sentence too.

Line 61. Define MMA here. Line 87. Please provide the explanation why this particular alloy has been selected among Al alloys. Line 207. What was the initial roughness of the as-prepared sample? Please specify. Line 202. The sample was 4 cm*2 cm (see line 104). How did you scratch it “2 cm from the sample edge” on the smaller side? Please check it. Table 2. Please provide peak assignments in the table. The FTIR section in Results should be thoroughly checked and corrected. It goes for grammar, some confusing phrases, and organization of the results. Line 344. I did not receive Fig. SI-1 with the submission. Line 381. Are 6% at% or wt%? Table 4 shows only 4% difference. Please check. Fig. 7c. How did the authors prove the formation of monovalence Si in the formed polymer? This is not clear for me how did this structure formed as this aspect is not discussed in the text. Is it possible at all. Authors should comment on it. Line 464. Please provide images of the surface contact angle measurements (It can be added to the supplementary). Line 501. Should be MHz I suggest adding equivalent circuits in the EIS section (as insets to the existing plots) and evaluate its main parameters. It can be also useful to calculate a decrease in the R and C parameters with time and calculate “degradation rate” of the coating. Please provide also the results of spectra fitting in Figures. Did the authors try to perform a salt spray test with the x-shape cut of the coating? It will also evaluate a long-term coating adhesion. Authors should compare the results of the physicochemical evaluation of the coatings (1^st part of the manuscript) with the corrosion section and provide an explanation why PEMA- and PMMA-coatings have different anticorrosion properties. In the conclusions section (lines 569–570) the difference in corrosion behavior is explained from the point of the thickness. Does it mean that both coatings with the same thickness are more or less the same and there is no obvious effect of Methyl and Ethyl Group on the corrosion behavior? The manuscript is entitled “The Effect of the Methyl and Ethyl Group…for Corrosion Protection of Aluminium Alloy 7075-T6” and I did not find a strong conclusion on this effect in the final part of the manuscript.

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors

 

  I would like to first appreciate your hard work in coming up with a manuscript which gives details on the use of siloxane-PMMA and siloxane-PEMA coatings for Al based substrate. The chemical and corrosion characterization are very extensive and detailed. However I would like to recommend your manuscript for minor revision to improve readability. Please see my below comments

1) The introduction is not very clear. There is too much content which I feel is not required. They have not provided any details of why these coatings would act differently if they are coated on aluminum vs steel. The manuscript claims that they are using these coatings as it’s not extensively used for Al-based material substrate. Is this novel enough?  

2) The abstract of the manuscript should start with the problem statement. I would like to request the authors to clearly state the problem, hypothesis, methods, results and conclusion concisely in the abstract.

3) There are not much details on mechanism involved in the coating's successfully inhibition of chloride corrosion.

 

Best wishes

 

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

the article is very interesting and of a high scientific quality. parts of the introduction are to big (lines 73-98) and need a reformulation as a shorter version; the entire chapter 2 is very well explained but also needs some reformulations; line 365 equation is 1 not 2- please correct. line 400: O-Si-Oi suppose to be O-Si-O , eliminate i line 420: Fig.7. It -Fig.7. it  line 615: Dos Santos suppose to be dos Santos 

Author Response

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Round 2

Reviewer 2 Report

I thank the authors for their replies to my comments. I found them satisfactory.

With my best regards,