Evaluation of Tannins as Potential Green Corrosion Inhibitors of Aluminium Alloy Used in Aeronautical Industry

Round 1

Reviewer 1 Report

The article highlights peculiarities of evaluation of tannins as potential green corrosion inhibitors of aluminium alloy used in aeronautical industry. The authors conducted a detailed assessment of the microstructure and corrosion properties of the coating on aluminium alloy AA2024-T3 anodized in CSA, GSA, MSA, TNSA bath, and anodized in CSA, GSA, MSA, TNSA bath and sealed.

The article is interesting, but a number of shortcomings need to be corrected:

1. The scale bar on the SEM images (Fig. 6-9) cannot be recognized.
2. The font size in Figs. 3, 4, 11-19 should be increased.
3. More new References (2019-2022) should be added.

Author Response

Dear reviewer,

Thank you for your comments. We accept all and we made the necessary changes in the manuscript as we detail bellow:

1. The scale bar on the SEM images (Fig. 6-9) cannot be recognized.

The SEM images (Fig. 6-9) were increased.

 

1. The font size in Figs. 3, 4, 11-19 should be increased.

The font size in Figs mentioned before were incresead.

 

1. More new References (2019-2022) should be added.

We introduced three new very recent references, published in 2021:

• Aourabi, S.; Driouch, M.; Sfaira, M.; Mahjoubi, F.; Hammouti, B.; Verma, C.; Ebenso, E.; Guo, L. Phenolic fraction of Ammi visnaga extract as environmentally friendly antioxidant and corrosion inhibitor for mild steel in acidic medium, Journal of Molecular Liquids, 2021, 23, 2021, 114950.
• Iroha, K.B.; Maduelosi, N. J. Corrosion Inhibitive Action and Adsorption Behaviour of Justicia Secunda Leaves Extract as an Eco‐Friendly Inhibitor for Aluminium in Acidic Media, Biointerface Research in Applied Chemistry, 2021, 11 (5), 13019-13030.
• Tan, B. ; Xiang, S.; Zhang, Qiang, Y.; Xu, L.; Chen, S.; He, J. Papaya leaves extract as a novel eco-friendly corrosion inhibitor for Cu in H2SO4 medium, Journal of Colloid and Interface Science, 2021, 582, 918-931.

Reviewer 2 Report

1. Fig.6 to Fig.9 can be merged to one figure.
2. In Fig.14, the fitting line looks not fit well. Which means that the equivalent circuit is not reasonable. Authors should choose the most reasonable circuit to fit the lines.
3. In 3.4 part, Why the phase angle changes? Please explain it.
4. Even though the authors did lots of works, they should summarize the results in a better way.
5. The authors should carefully check the whole manuscript, including the expression and grammar.

Author Response

Dear reviewer,

Thank you for your comments. We accept all and we made the necessary changes in the manuscript as we detail bellow:

 

1. Fig.6 to Fig.9 can be merged to one figure.

The Fig.6 and Fig 9 were merged to one figure.

 

2. In Fig.14, the fitting line looks not fit well. Which means that the equivalent circuit is not reasonable. Authors should choose the most reasonable circuit to fit the lines.

We increase the size of the figure 14.

The equivalent circuit presented in the manuscript was selected based in the literature, as it is explained in the main text. We choose this circuit since other circuits were also tested and, from the analysis to the results obtained, we concluded that this circuit, besides being the circuit that presented a better approximation between fitting and the experimental results, was also the one in which the fitting results presented a greater coherence and meaning over the immersion time.

 

3. In 3.4 part, Why the phase angle changes? Please explain it.

 

This information was added in the revised form of the manuscript in section 3.4:

“In the same time, slight shifts of phase-angle was observed during the immersion time. This behaviour may be due to the increase the corrosion phenomenon promoted by the contact with the corrosive agents.”

 

4. Even though the authors did lots of works, they should summarize the results in a better way.

Conclusions were reformulated to include an overview of the results obtained.

 

5. The authors should carefully check the whole manuscript, including the expression and grammar.

We improve the expression and grammar in the revised manuscript.

Reviewer 3 Report

Dear authors,

I enjoyed reading the manuscript because the paper is well-described, and the results are clearly demonstrated. ​ The author made a good synthesis of literature that provides an overview of the research evolution in this area.

 

This manuscript, entitled „Evaluation of tannins as potential green corrosion inhibitors of aluminium alloy used in aeronautical industry” is relevant to the scope of this journal. This is an interesting study that can provide interesting information to specialists.

Therefore, the article can be recommended for publication only after mandatory revision according to the following suggestions:

1. A better visibility of the scale in Figures 6-9 would be preferable.
2. If an equivalent circuit model with two constant phase elements (CPE) is proposed in Figure 18b, then they must be otherwise symbolized. They cannot have a symbol like the capacitors in Figure 18a.
3. The errors obtained after fitting the experimental data using the proposed equivalent electrical circuits should be specified. For example, in Figure 14b, the error appears to be relatively large.
4. I think that in the legend of Figure 19 there is a mistake because Rp appears twice. I think the presentation of the data from Figures 19 in the form of a table would be more eloquent.
5. In order to claim that the presence of tannins in baths conversion increases corrosion resistance, corrosion tests should also be performed. Perhaps a recording of potentiodynamic polarization curves with corrosion rate determination would be indicated. Or at least a determination of the corrosion rate values from the EIS data obtained should be made.

Author Response

Dear reviewer,

Thank you for your comments. We accept all and we made the necessary changes in the manuscript as we detail bellow:

Therefore, the article can be recommended for publication only after mandatory revision according to the following suggestions:

1. A better visibility of the scale in Figures 6-9 would be preferable.

The SEM images (Fig. 6-9) were increased.

2. If an equivalent circuit model with two constant phase elements (CPE) is proposed in Figure 18b, then they must be otherwise symbolized. They cannot have a symbol like the capacitors in Figure 18a.

We correct the legend in Figure 18b.

3. The errors obtained after fitting the experimental data using the proposed equivalent electrical circuits should be specified. For example, in Figure 14b, the error appears to be relatively large.

We agree and introduced the errors obtained in the fitting in the Figure 16.

4. I think that in the legend of Figure 19 there is a mistake because Rp appears twice. I think the presentation of the data from Figures 19 in the form of a table would be more eloquent.

We correct and increase the legend in Figure 19.

5. In order to claim that the presence of tannins in baths conversion increases corrosion resistance, corrosion tests should also be performed. Perhaps a recording of potentiodynamic polarization curves with corrosion rate determination would be indicated. Or at least a determination of the corrosion rate values from the EIS data obtained should be made.

We agree with your comment and the potentiodynamic polarization curves were included in the revised form of the manuscript.

 

Round 2

Reviewer 2 Report

It is ok to be accepted.

Reviewer 3 Report

In my opinion, the authors have made all the required corrections and additions, so that the manuscript now has a much improved form that can be recommended for publication.