Non-Linear Evaluation of Coatings Performance: Evaluation of Polyester/Melamine Coil Coating Hydrolysis in NSS Test

Round 1

Reviewer 1 Report

1.      The definition of f should be added in line 122.

2.      Some spelling and grammar mistakes need to be corrected, like line 191, line 169, 178, 219, 264, 273, etc.

3.      The exposed area for working electrode should be given.

4.      Each time constant corresponds to the detailed process, which owe to be introduced.

5.      As for Table 1, variance about the fitted parameters should be added. The following reports can be cited, like:

(1)    Wan, S., Chen, H., Cai, G., Liao, B., & Guo, X. (2022). Functionalization of h-BN by the exfoliation and modification of carbon dots for enhancing corrosion resistance of waterborne epoxy coating. Progress in Organic Coatings, 165, 106757.

(2)    Zeng, Q., Min, X., Luo, Z., Dai, H., & Liao, B. (2022). In-situ preparation of superhydrophobic Zn-Al layered double hydroxide coatings for corrosion protection of aluminum alloy. Materials Letters, 328, 133077.

6.      The unit of parameters in Fig. 9 should be given.  

Minor editing of English language required.

Author Response

Reviewer 1 (yellow color in the text)

1.The definition of f should be added in line 122.

Definition of “f” was included

2.Some spelling and grammar mistakes need to be corrected, like line 191, line 169, 178, 219, 264, 273, etc.

Spelling and grammar mistakes were corrected

3.The exposed area for working electrode should be given.

Samples exposed at different times were cut and six 1.5 cm² pieces were obtained for every time of exposure. Three pieces were used for EIS measurements and the other three for EN measurements. Exposed area was 1 cm²

4.Each time constant corresponds to the detailed process, which owe to be introduced.

In figure 5 the meaning of the components of the electrochemical equivalent circuit was modified.

5. As for Table 1, variance about the fitted parameters should be added.

The value of Chi square was added

 

The following reports can be cited, like:

(1)Wan, S., Chen, H., Cai, G., Liao, B., & Guo, X. (2022).Functionalization of h-BN by the exfoliation andmodification of carbon dots for enhancing corrosionresistance of waterborne epoxy coating. Progress inOrganic Coatings, 165, 106757.

(2) Zeng, Q., Min, X., Luo, Z., Dai, H., & Liao, B. (2022). In-situ preparation of superhydrophobic Zn-Al layered doublehydroxide coatings for corrosion protection of aluminumalloy. Materials Letters, 328, 133077.

The above reports were added as references

6.The unit of parameters in Fig. 9 should be given.

It is not possible; the parameters are dimensionless.

 

Reviewer 2 Report

.The paper entitled ‘Non-linear Evaluation of Coatings Performance. Evaluation of Polyester/melamine Coil Coating Hydrolysis in NSS Test’ as a whole seems more or less like a technical report for a manufacturer of protective coatings rather than a scientific article.

My comments are as follows:

- The authors in section 3.3. electrochemical tests (EIS and EN) state...

'Bode and Nyquist diagrams obtained at different exposure times in NSS are presented in Figure 4.',…….. but there are no Nyquist plots here... these should be added with appropriate comments and discussion.

- Nyquist and Bode diagrams should show fitting curves of the experimental points. On the contrary, it is not possible to conclude the adequacy of the equivalent circuit. They should be added. Also, there is no data of the error of the fitting procedure  2 which confirms the suitability of the Equivalent Electrical Circuit (EEC) used. On the basis of all of them, the appropriateness of the used equivalent circuit can be confirmed or reject.

- In Figure 4 the frequency values are unusual, missing the negative sign to the left of 1 in the exponent, otherwise the quality of Figure 4 is at an extremely low level. The authors should improve this.

- It is also obvious from Figure 4 (of course, only if one imagines the correctly represented value of the frequencies on the x-axis) that the selected frequency range only up to 0.05 Hz is too coarse for most measurements. It is clear that the process is not yet complete. At least up to a frequency of 0.005 or even 0.001 Hz would have to be measured, especially since the authors speak of diffusion processes characterized by a low frequency range.

- The authors specify 'capacitance..." The correct units for this are F/cm² or (micro-, nano-, pico-farads per square centimeter) and not Ω −1 cm −2 sNc as they write.

-What the authors give either (YDL) or CPE are only the values of the elements contained in the electrical equivalent circuit (EEC). In the EEC, the designations YDL and YC are used, while the text refers to CPE. The authors should choose one of the two designations.

-If the authors have taken the values of the CPE element directly from the 'fitting procedure', it is not a real capacity (C). The values of the CPE element must be recalculated according to the following formula:

??=[(??????)1??⁄] ??⁄

where 'x' represents the number for each RC- loop in the EEC (x =1,2 …). Each CPE in the equivalent circuits should be separately calculated.

The paper entitled ‘Non-linear Evaluation of Coatings Performance. Evaluation of Polyester/melamine Coil Coating Hydrolysis in NSS Test’ as a whole seems more or less like a technical report for a manufacturer of protective coatings rather than a scientific article.

My comments are as follows:

- The authors in section 3.3. electrochemical tests (EIS and EN) state...

'Bode and Nyquist diagrams obtained at different exposure times in NSS are presented in Figure 4.',…….. but there are no Nyquist plots here... these should be added with appropriate comments and discussion.

- Nyquist and Bode diagrams should show fitting curves of the experimental points. On the contrary, it is not possible to conclude the adequacy of the equivalent circuit. They should be added. Also, there is no data of the error of the fitting procedure  2 which confirms the suitability of the Equivalent Electrical Circuit (EEC) used. On the basis of all of them, the appropriateness of the used equivalent circuit can be confirmed or reject.

- In Figure 4 the frequency values are unusual, missing the negative sign to the left of 1 in the exponent, otherwise the quality of Figure 4 is at an extremely low level. The authors should improve this.

- It is also obvious from Figure 4 (of course, only if one imagines the correctly represented value of the frequencies on the x-axis) that the selected frequency range only up to 0.05 Hz is too coarse for most measurements. It is clear that the process is not yet complete. At least up to a frequency of 0.005 or even 0.001 Hz would have to be measured, especially since the authors speak of diffusion processes characterized by a low frequency range.

- The authors specify 'capacitance..." The correct units for this are F/cm² or (micro-, nano-, pico-farads per square centimeter) and not Ω −1 cm −2 sNc as they write.

-What the authors give either (YDL) or CPE are only the values of the elements contained in the electrical equivalent circuit (EEC). In the EEC, the designations YDL and YC are used, while the text refers to CPE. The authors should choose one of the two designations.

-If the authors have taken the values of the CPE element directly from the 'fitting procedure', it is not a real capacity (C). The values of the CPE element must be recalculated according to the following formula:

??=[(??????)1??⁄] ??⁄

where 'x' represents the number for each RC- loop in the EEC (x =1,2 …). Each CPE in the equivalent circuits should be separately calculated.

Author Response

Reviewer 2 (green color in the text)

- The authors in section 3.3. electrochemical tests (EIS and EN) state...

'Bode and Nyquist diagrams obtained at different exposure times inNSS are presented in Figure 4.',…….. but there are no Nyquist plots here... these should be added with appropriate comments and discussion.

 

Nyquist plots were included with appropriate comments and discussion.

- Nyquist and Bode diagrams should show fitting curves of the experimental points. On the contrary, it is not possible to conclude the adequacy of the equivalent circuit. They should be added. Also, there is no data of the error of the fitting procedure # 2 which confirms the suitability of the Equivalent Electrical Circuit (EEC) used. On the basis of all of them, the appropriateness of the used equivalent circuit can be confirmed or reject.

The value of Chi square was added

 

 

- In Figure 4 the frequency values are unusual, missing the negative sign to the left of 1 in the exponent, otherwise the quality of Figure 4 is at an extremely low level. The authors should improve this.

The two Bode and Nyquist diagrams were included and the missing signs were corrected

Figure 4 was improved

- It is also obvious from Figure 4 (of course, only if one imagines the correctly represented value of the frequencies on the x-axis) that the selected frequency range only up to 0.05 Hz is too coarse for most measurements. It is clear that the process is not yet complete. At least up to a frequency of 0.005 or even 0.001 Hz would have to be measured, especially since the authors speak of diffusion processes characterized by a low frequency range.

Our system did not allow us to reach lower frequencies since there was dispersion in the data.

 

- The authors specify 'capacitance..." The correct units for this are F/cm² or (micro-, nano-, pico-farads per square centimeter) and not Ω −1 cm −2 sNc as they write.

::::::::: As is known, a CPE is defined by the following equation containing Y a constant independent of the frequency and N an exponential that defines the type of element present, when it corresponds to a capacitor Y has a value directly proportional to the capacitance involved

 

 

-What the authors give either (YDL) or CPE are only the values of the elements contained in the electrical equivalent circuit (EEC). In the EEC, the designations YDL and YC are used, while the text refers to CPE. The authors should choose one of the two designations.

As is known, a CPE is defined by the following equation containing Y a constant independent of the frequency and N an exponential that defines the type of element present, for example 0.5 a diffusion and greater than 0.5 to 1 would correspond to a capacitor, this nomenclature is maintained so that the reader can more easily relate the elements involved

CPE= Y(Jw)^N

 

-If the authors have taken the values of the CPE element directly from the 'fitting procedure', it is not a real capacity (C). The values of the CPE element must be recalculated according to the following formula:

??=[(??????)1??⁄] ??⁄

where 'x' represents the number for each RC- loop in the EEC (x=1,2 …). Each CPE in the equivalent circuits should be separately calculated.

It was not recalculated because a CPE can represent a capacitor, an inductor, a resistor or a diffusion. In our case when N was greater than 0.5 it would be a capacitor with an irregular surface and Y is directly proportional to the capacitance and when N equals 0.5 diffusion as happened in our case depending on the conditions

CPE= Y(Jw)^N

Reviewer 3 Report

This paper mainly addressed the advantages of using EN in evaluating corrosion. The strength of this paper is that the approach is interesting point of view as EN and RP are not relatively new, but it is not widely used in corrosion performance assessment. 

Some suggestion as minor correction:

1. Some detailed explanation on how delamination taking place should be added. 

2. What is the goodness of fitting obtained for the EIS?

3. Some of the abbreviations used are not defined to the readers, eg: NDL, Yc etc. 

4. Check for typo, eg: Page 8, line 269: Rt and Rn (was it Rct?). please check for typo on several figure captions.

5. Some of the claims in this work needs some support/verification from literature. 

6. It is interesting to see that EN shows faster/more sensitive results compared to EIS. 

 

7. The references appropriate.

 

 

 

Author Response

Reviewer 3 (clear blue in the text)

1. Some detailed explanation on how delamination taking place should be added.

In the samples evaluated no delamination is observed, it is only detected by changes in electrochemical behavior.

What is relevant about the methodology exposed in the article is its sensitivity, since a uniform corrosion phenomenon is observed at a given moment after 1000 hours, which could only occur when the coating is completely separated from the metal surface.

2. What is the goodness of fitting obtained for the EIS?

The value of Chi square was added to table 1

 

3. Some of the abbreviations used are not defined to the readers, eg: NDL, Yc, etc.

In the legend of figure 5 all the terms of the equivalent circuit that was used are defined.

3. Check for typo, eg: Page 8, line 269: Rt and Rn (was it Rct?) please check for typo on several figure captions.

Rct corresponds to charge transfer resistance

Rn corresponds to electrochemical noise resistance

 

5. Some of the claims in this work needs some support/verification from literature.

Three new references were added: 8, 9 and 37

6. It is interesting to see that EN shows faster/more sensitive results compared to EIS.

That was the main objective of this investigation.