Research on Corrosion Damage Evolution of Aluminum Alloy for Aviation

Round 1

Reviewer 1 Report

I recommend the authors to modify the text according to the corrections in the attached file. I recommend thinking about the statement that it is an erosion, see the description in the attached file. After editing, I recommend the article for publication.

Comments for author File: Comments.PDF

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The authors prepared an interesting research paper on the advanced evaluation of corrosion attack on 7075 aluminium alloy in an original simulated environment in short exposure stages. The quality of experimental works is sufficient, however, there are some important and questionable areas that need to be clarified or corrected.

1. page 1, Line 16: I suggest to use „corrosion pits“ instead of „pitting pits“ in a whole document.
2. page 1, line 37: The sentence: “Aluminum alloy materials on the surface of aircraft body” is not complete.
3. page 4, line158-159: Authors claim: “Since there is no corrosion test chamber for controlling humidity by saturated salt solution, this test is conducted by manual method.” How did you manually control and maintain the humidity of the system during the whole drying period in a chamber without the assistance of the chamber system? Especially, in a case, when you are putting the samples into the chamber. The air is ventilated and mixed with the surrounding atmosphere in seconds. So, how did you manually increase and maintain the humidity to exactly 87.6%
4. page 5, line 164: The sentence: “When the pH changes” is not complete.
5. Page 6, line 202: the sentence: “when the accelerated corrosion time is 72h and 96h, the specimen has lost metal” is not complete.
6. Authors aimed to create a more truly accelerated corrosion test compared to EXCO, changed some process parameters, and performed the test. In Conclusions, the authors claim that the traditional immersion corrosion method was improved. However, I cannot find any evidence in the paper supporting this claim. There is no comparison between the level of correlation of standard EXCO method and suggested one to real outdoor exposure results. Without the evidence, that the presented method better simulates real corrosion processes on samples in Wanning area of Hainan Province than a traditional standard, the presented results are not of wide interest. Hence, the above-mentioned comparison needs to be added to the paper.

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

This paper presents novel and interesting model to evaluate pitting pit depth and pitting rate. However,  there is a few concerns on interrupting the results and implementing the results so the novelties of the paper can be seen. Also, the structure of the paper needs to be improved, it is very difficult to follow it. Furthermore, an extensive editing of English language and style required. This paper could be published if some improvements can be made and the concerns can be clarified.

Abstract;

The novelty of the paper is not clear from the Abstract. What do you mean with “traditional alternate immersion corrosion test? Please be more specific.

Introduction;

Line 37: The sentence “Aluminium alloy..” not finished.

Line 38: Please rewrite these sentence, it is not clear.

Line 40: More references are needed, since you are mention many studies.

Line 54: The sentence “The new version…” is too loge. Please rewrite.

Line 65: “micron scale” should be replaced with “micro scale”.

Line 79: Which technique you used for 3D profile measurements? Please be more specific.

General:

In the introduction is missing the description of previous studies which were dealing with similar topic. It should be clear what was done till now and what you did that make your work so novel. Also describe better the atmospheric corrosion in Wanning, why is so corrosive and why you chose Wanning. Also some more background regarding evaluation of pits (parameters Cr, d) is required for the audience which is not so specialized in this field.

Materials and Methods;

Line 87: Space after Table 1 is needed.

General:

So many abbreviations are used, such as NC, GB / T 6398- 88 2000. hey have to be explained. How you measured surface roughness-Ra? Please explain. Figure 1 should be explain in details. Is this your design or it is from the reference? If it is your please explain each parameter in the Figure1. Also, in the section of Materials chemicals that you used should be listed.

Methods:

General:

Techniques/methods are deficient described and should be improved. Names of software, equipment, instrument used should be added and described (brands, specifications). Which are alternative immersion corrosion methods? Please be more specific. Technique or method used for 3D measurements should be describe in details. All steps. Maybe a schematic representation (steps of work you used) would be better, with all steps used in this work, since now is very difficult to follow.

Lines 96-103: Should be in Introduction.

Lines 104, 105: Not clear what is 1.? Why the 1. is not described as 2.?

Line 115; Table 2: Too many decimals, max 2 and please in the whole table is should be unique.

Line 212: Please describe Herry’s law.

Lines 124-134: Some references more.

Line 173: Figure 3: Not clear to me. What are a) and b)? They should be in the Figure and not below?

Line 179: 0.95 hours and 7.06 hours, very strange. Better 1h and 7h.

Results and discussion:

Line 187: “Corrosion appearance” should be replace with “Corrosion evaluation”.

Line 196: Figure 5: Scale bars are missing on all images. It looks for me that this is not the same sample? The dimension of them does not look the same. Please specify if you tested different samples. Yellow color of time should be replaced with more visible color.

Line 218: Very bad quality of left image (3D). Also the 3D result have to be better explained.

Figure 221: 2.2.1: The part where you describe method should go in Methods section and not in the Results.

General:

How did you fit your results? It should be described. Maybe would be easier to follow if you make a schematic representation in Methods. Binary morphology should be explain in Methods in details. Which technique was used for to obtain binary images? Please describe it in methods, Also which technique was use to obtain left images in Figure 13? If SEM or any other microscopy please describe it in methods. Also, the scale bar is missing on all images in Figure 13.

Conclusions:

Line 363: Why you suddenly use cyclic corrosion immersion instead alternate? Is this the same?

(2) Where you provided statistical analysis? Gumbel Weibull distribution should be better explain in Introduction if you are using them for conclusions.

General:

It is not really clear what are the main advantages of herein used technique compared to others. You are mention great improvement, so please specify.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The authors successfully corrected or explained 4/5 of my comments. However, I still miss any statement about the comparison of presented modified accelerated corrosion test to standard EXCO method (or modyfied EXCo method acc. to: S. Lee and B. Lifka, "Modification of the EXCO Test Method for Exfoliation Corrosion Susceptibility in 7XXX, 2XXX, and Aluminum-Lithium Alloys," in New Methods for Corrosion Testing of Aluminum Alloys, ed. V. Agarwala and G. Ugiansky (West Conshohocken, PA: ASTM International, 1992), 1-19. ) or real exposure results in Wanning area of Hainan Province that would prove the authors' conclusion that presented method is more suitable for 7075 alloy testing.

On the other hand, the presented research is mainly dealing with modern method of more effective evaluation of pitting corrosion on aluminium alloys, so there is an option to recompose the overall motivation and focus of the paper to present the modern method of evaluation of the results rather than on improving the existing standard. After that, it could be accepted. However, the main goal of the paper in the present form (improving the EXCO standard) is not reached as there is no direct evidence presented in the paper supporting this claim by comparing the results to the original method.

 

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

I believe that manuscript has been significantly improved and warrants publication in Applied Sciences.

Author Response

Thank you  for affirming my paper，best wishes to you.

Round 3

Reviewer 2 Report

I am glad, that the authors have understood my major suggestion and edited the manuscript into an acceptable form. Of course, the paper could be still improved to a higher quality level to be more attractive for readers, however, it is suitable for publication in the present form.

I wish a good luck and a lot of success in your future work!