Development of a Reliable Accelerated Corrosion Test for Painted Aluminum Alloys Used in the Aerospace Industry

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This article compare different accelerated corrosion tests with natural exposure test in marine environment in the field of the corrosion of painted aeronautic aluminium alloys.

This kind of article is rare, very interesting and should be published.

Nevertheless, the article is quite difficult to read and should be improved to be published.

Many figures could be homogenised and improved by adding correct labelling of axis and captions. The different terms (or wording) and numbering should be also homogeneized all along the article.

The discussion and conclusions remain very descriptive. A discussion about the conditions of accelerated test to mimic a natural marine exposure seems to be possible.

In introduction:

 Why do you use the ASTM B117 standard in replacement of the ISO9227 standard ?

In 2.1 section :

Can you precise the overall thickness of the protective system ?

In 2.3.1 section:

The description of the Volvo cycle is very difficult to understand. In the text, you say that there are 2 pollutions phases during the 6 h of salt rain. In the Figure 1, you note that there are 3 period of 15 minutes at 15 mm/h and/or at 120 mL/h/80 cm2 .  Can you describe with accuracy the salt rain period and all the test ?

For the Volvo test, at the beginning of page 4, what is the "Volvo VCS 1027, 149" ? Is it the Volvo STD 423-0014 test of the Figure 1 ? Please can you clarify.

I suppose that the second 2.3.1 section should be labelled 2.3.2 section (Accelerated corrosion test-Design of experiment (DoE) )

In the Accelerated corrosion test-Design of experiment (DoE) section:

What are the  "VCS 1027,149 wet and dry cycles"?

You use the word "test" to describe a "corrosion test", the NSSS or the volvo test, and you also use the word "test" to describe the different trials of the DoE. So the reading is quite difficult.

Can you note on graphs (figure 1 and/or figure 2) the variable of your DoE : WT and WTH ? If I have well-understood, the wet temperature and the dry temperature are already constant for all trials ?

In 2.4 section :

What is the "scribe" ? is it the scratch ?

In results section:

All along the article, can you complete with accuracy the label of axis of the figures in bars ?

In some part, you speak about the "exposed samples number" (in Table 1), and in other part you speak about the "painted sample number" (in Table 6 and others). It the same ?

In discussion/conclusion:

What are the acceleration factor and the coefficient of variation of the other trials ?

Why the WRH should be high ? at 95%

The article must be corrected and carefully read again (and re-work) to improve its understanding. A beginning of discussion could develop the conclusions.

 

 

 

 

 

Author Response

Please find the answers to the reviewer comments written in red under or next to his comments. In the revised paper, you will also find all the changes written in red.

Kind regards

Fabienne Peltier

 

In introduction:

 Comments 1 : Why do you use the ASTM B117 standard in replacement of the ISO9227 standard ?

Response 1 : It is the same standard for neutral salt spray test.

In 2.1 section :

Comments 2: Can you precise the overall thickness of the protective system ?

Response 2 :This was added to the publication

In 2.3.1 section:

Comments 3: The description of the Volvo cycle is very difficult to understand. In the text, you say that there are 2 pollutions phases during the 6 h of salt rain. In the Figure 1, you note that there are 3 period of 15 minutes at 15 mm/h and/or at 120 mL/h/80 cm2 .  Can you describe with accuracy the salt rain period and all the test ?

Response 3: The description has been improved in the publication

Comments 4: For the Volvo test, at the beginning of page 4, what is the "Volvo VCS 1027, 149" ? Is it the Volvo STD 423-0014 test of the Figure 1 ? Please can you clarify.

Response 4: It was a mistake of designation. It has been modified in the publication

Comments 5: I suppose that the second 2.3.1 section should be labelled 2.3.2 section (Accelerated corrosion test-Design of experiment (DoE) )

Response 5: Yes, it has been modified

In the Accelerated corrosion test-Design of experiment (DoE) section:

Comments 6: What are the  "VCS 1027,149 wet and dry cycles"?

Response 6: It is the cycle of the VCS 1027,149 presented in fig 1.

Comments 7: You use the word "test" to describe a "corrosion test", the NSSS or the volvo test, and you also use the word "test" to describe the different trials of the DoE. So the reading is quite difficult.

Response 7: I tried to improve this part

Comments 8: Can you note on graphs (figure 1 and/or figure 2) the variable of your DoE : WT and WTH ? If I have well-understood, the wet temperature and the dry temperature are already constant for all trials ?

Response 8: It has been added in the publication

In 2.4 section :

Comments 9: What is the "scribe" ? is it the scratch ?

Response 9: Yes

In results section:

Comments 10: All along the article, can you complete with accuracy the label of axis of the figures in bars ?

Response 10: It was completed

Comments 11: In some part, you speak about the "exposed samples number" (in Table 1), and in other part you speak about the "painted sample number" (in Table 6 and others). It the same ?

Response 11: yes

In discussion/conclusion:

Comments 12: What are the acceleration factor and the coefficient of variation of the other trials ? Response 12: These information were added in a table in replacement of the graph .

Comments 13: Why the WRH should be high ? at 95%

Response 13: A WRH of 95% seems to be the most appropriate to mimic field exposure. Indeed, A high humidity generate mainly blistering as it was observed in field.

 

 

 

Thank you for taking the time to read my publication.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Authors performed extensive corrosion tests on 8 different preparations of painted aluminum alloys (mainly AA2024), using 3 different accelerated corrosion standard test methods (ASTM B117, ISO 4623-2, VCS 1027,149), and compared the results with each other and with the results of the 5 year field exposures in a marine atmospheric site. The results of the work are very interesting and important conclusions concerning correlations between the results of the accelerated corrosion tests and the 5 year field exposures, the influence of the test method on the morphology of corrosion (filaments versus blisters) and the corrosion susceptibility assessment were drawn. Author also proposed some modifications of the VCS 1027,149 test which increases the agreement between the results of the accelerate test and the 5 year field exposure.

Manuscript is written in rather bad English (with the exception of the Abstract), some sentences are difficult to be understood. English is not my mother language; authors should ask a professional translator or a native speaker to improve English of their manuscript.

The tittle of the paper (Development of a reliable accelerated corrosion test for painted aluminium alloys used in the aerospace industry) does not reflect the content of the article. Authors have not developed any really new corrosion test but only made some modifications in already known VCS 1027, 149 test by varying several test parameters. I propose the tittle: “Evaluation of the reliability of accelerated corrosion tests for painted aluminium……..”

Equation 1 is not written according to the rules. Name of a variable (Const.) should not contain period. What is x? If it is multiplication mark, it should be removed.

Authors write:” The data indicated that extremely low propagation of underpaint corrosion occurred after 3000 h of NSST……………….. Nevertheless, system 1 which shows the largest extent of underpaint corrosion is very likely sensitive to high humidity as NSST provides permanent wet conditions.” It is not the system 1, but the system 2 that showed the largest extent of underpaint corrosion.

Authors write:” As further inferred from Figure 3, systems involving a Cr free primer e.g. 1  and 2 seem to be the least resistant ones.” System 7 is even less resistant one!

Authors write:” Table 8 emphasizes the differences in failure modes observed when comparing NSST and ISO 4623-2 with the accelerated corrosion tests. I do not understand: are not NSST and ISO 4623-2 tests the accelerated corrosion tests?

Comments on the Quality of English Language

Some sentences are written in a complicated style and could be much better understandable if corrected. Authors should ask a professional translator or a native speaker to improve English of their manuscript.

 

Author Response

Please find the answers to the reviewer comments written in red under or next to his comments. In the revised paper, you will also find all the changes written in red.

Kind regards

Fabienne Peltier

 

Comments 1: The tittle of the paper (Development of a reliable accelerated corrosion test for painted aluminium alloys used in the aerospace industry) does not reflect the content of the article. Authors have not developed any really new corrosion test but only made some modifications in already known VCS 1027, 149 test by varying several test parameters. I propose the tittle: “Evaluation of the reliability of accelerated corrosion tests for painted aluminium……..”

Response 1: I understand your comment, but the idea of this work is to develop a new test for the aerospace industry even if it is developed from an existing test. The results presented in this publication are part of a large project aimed at a standardization.

Comments 2: Equation 1 is not written according to the rules. Name of a variable (Const.) should not contain period. What is x? If it is multiplication mark, it should be removed.

Response 2: It has been modified in the publication

Comments 3: Authors write:” The data indicated that extremely low propagation of underpaint corrosion occurred after 3000 h of NSST……………….. Nevertheless, system 1 which shows the largest extent of underpaint corrosion is very likely sensitive to high humidity as NSST provides permanent wet conditions.” It is not the system 1, but the system 2 that showed the largest extent of underpaint corrosion.

Response 3: The modification was done

Comments 4: Authors write:” As further inferred from Figure 3, systems involving a Cr free primer e.g. 1  and 2 seem to be the least resistant ones.” System 7 is even less resistant one!

Response 4: The modification was done

 

Comments 5: Authors write:” Table 8 emphasizes the differences in failure modes observed when comparing NSST and ISO 4623-2 with the accelerated corrosion tests. I do not understand: are not NSST and ISO 4623-2 tests the accelerated corrosion tests?

 

Response 5: Yes, they are, but they are standardized accelerated corrosion tests at the difference of the tests developed in the DoE

 

Thank you for taking the time to read my publication.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

 The discussion of the effects of conditions of tests on the corrosion is poor but I accept the corrections. The results of article remain very interesting, but the scientific interpretations remains weeak.