A Comparative Study on the Influence of Al2O3-ZnO ALD Nanolaminates on the Properties of CrCN PVD Sputtered Coatings with Distinctive Morphologies and Microstructures
, Syreina Sayegh 3, Mikhael Bechelany 3, Roland Habchi 2,4 and Akram Alhussein 1,*Round 1
Reviewer 1 Report
The presented manuscript looks interesting to the target audience. It may be accepted for publication after some improvements that are listed below.
1. Fig. 2. Adding elemental mapping in elemental contrast will add some value to the figure. Also, do not forget to discuss the distribution of elements within the text of the manuscript.
2. Fig. 4. Please, point phases from the main planes, otherwise these XRD spectra look useless.
3. Fig. 5. This figure looks a little bit confusing to me. I would like to propose providing H and E separately, as well as including the measurement errors.
4. Fig. 6. I would like to propose adding an approximation of smoothing lies here to make it more clear and more visible.
5. The review of recently published articles devoted to similar topics looks incomplete. I would like to propose paying attention to the work [1], probably, the authors of the manuscript will find them worth mentioning.
Reference
[1] Materials and Design, 2018, Vol. 153, pp. 47-59.
I've detected some minor errors, thus I would like to recommend the authors of the manuscript to go through the text one more time to check it. Probably, the usage of Chat GPT will also help.
Author Response
We would like to thank the reviewer 1 for the precious comments and recommendations. We carefully revised the paper and corrected it. We have taken into account the highlighted remarks and the paper is now well enhanced in this revised version.
The presented manuscript looks interesting to the target audience. It may be accepted for publication after some improvements that are listed below.
- Fig 2. Adding elemental mapping in elemental contrast will add some value to the figure. Also, do not forget to discuss the distribution of elements within the text of the manuscript.
Answer: We totally agree with reviewer but unfortunately we cannot do that for many reasons: 1) the PhD student is no more in the lab, 2) the journal’s editor ask us to resubmit the revised version urgently, 3) and we estimate that all the elemental compositions are clearly presented in table 1. The distribution of the elements is homogenous in the coatings.
- Fig 4. Please, point phases from the main planes, otherwise these XRD spectra look useless.
Answer: All the XRD peaks correspond to the CrN phase except those relative to Cr adhesion layer where it is labeled “Cr” directly on the figure.
- Fig 5. This figure looks a little bit confusing to me. I would like to propose providing H and E separately, as well as including the measurement errors.
Answer: H and E are provided now in Table 3 in the revised version (including the standard deviation).
- Fig 6. I would like to propose adding an approximation of smoothing lies here to make it more clear and more visible.
Answer: We gave the values of contact angles clearly in the figure 6. Moreover, we mentioned the effect of surface smoothing in the manuscript.
- The review of recently published articles devoted to similar topics looks incomplete. I would like to propose paying attention to the work [1], probably, the authors of the manuscript will find them worth mentioning. Reference [1] Materials and Design, 2018, Vol. 153, pp. 47-59.
Answer: We thank the reviewer 1 for drawing our attention to this important publication. Now, it is cited in the revised manuscript [19].
Comments on the Quality of English Language
I've detected some minor errors, thus I would like to recommend the authors of the manuscript to go through the text one more time to check it. Probably, the usage of Chat GPT will also help.
Answer: The manuscript was carefully revised and the small mistakes were corrected.
Reviewer 2 Report
1. Some spelling and grammar errors need to be revised, like line 207, 516, 468, etc.
2. In the NaCl solution, cathodic reaction for corrosion is oxygen reduction. The Tafel extrapolation method can be not suitable due to that corrosion rate is controlled under activated control. Moreover, the detailed information about the fitting process for cyclic polarization curve is needed.
3. The relevant information obtained from Tafel slopes of anodic and cathodic reactions need to be added.
4. The definition of Rp should be added, and please explain why Rp and Jcorr both decrease for CrCN-2/ALD compared with those of CrCN-2.
5. Relevant work can be cited to analyze the anti-corrosion performance, like:
(1) Liao, B.*, Luo, Z., Wan, S., & Chen, L. (2023). Insight into the anti-corrosion performance of Acanthopanax senticosus leaf extract as eco-friendly corrosion inhibitor for carbon steel in acidic medium. Journal of Industrial and Engineering Chemistry, 117, 238-246.
6. The conclusion section can be divided into two parts.
Minor editing of English language required.
Author Response
Responses to Editor and Reviewers’ comments
We thank the editor and reviewers for their precious remarks and comments. We have taken into account all the highlighted recommendations. The revised manuscript is well enhanced. Here below our responses to the reviewer 1:
- Some spelling and grammar errors need to be revised, like line 207, 516, 468, etc.
Answer: We thank the reviewer 1 for the important remarks. The paper was carefully revised and the minor mistakes were corrected.
- In the NaCl solution, cathodic reaction for corrosion is oxygen reduction. The Tafel extrapolation method can be not suitable due to that corrosion rate is controlled under activated control. Moreover, the detailed information about the fitting process for cyclic polarization curve is needed.
Answer: No apparent Tafel region exists in the cathodic polarization curve, indicating the cathodic reaction is affected by activation control and diffusion control. The following paragraph was added to the characterization section in the revised version.
“As the diffusion limited region can be identified by observing a plateau in the current density as the potential is increased, the corrosion current density can be estimated by extrapolating the anodic branch of the polarization curve to the corrosion potential. The extrapolation involves fitting the anodic polarization curves to straight line and extrapolating it to the corrosion potential. The point at which these lines intersect gives the corrosion current density.”
- The relevant information obtained from Tafel slopes of anodic and cathodic reactions need to be added.
Answer: It is ok. They were used in the determination of the Rp.
- The definition of Rp should be added, and please explain why Rpand Jcorr both decrease for CrCN-2/ALD compared with those of CrCN-2.
Answer: More information is added in the characterization section. The decrease in the Jcorr is relative to the ALD insertion. The Rp didn’t show a large difference; it’s better to say it is in the same range of that of CrCN 2 coating if we take the uncertainty in consideration.
- Relevant work can be cited to analyze the anti-corrosion performance, like:
(1) Liao, B.*, Luo, Z., Wan, S., & Chen, L. (2023). Insight into the anti-corrosion performance of Acanthopanax senticosus leaf extract as eco-friendly corrosion inhibitor for carbon steel in acidic medium. Journal of Industrial and Engineering Chemistry, 117, 238-246.
Answer: We thank the reviewer 1 for the important suggested paper. This paper is well cited in the revised version.
- The conclusion section can be divided into two parts.
Answer: We agree with the reviewer 1. It has been done in the revised version.
Reviewer 3 Report
In their article, the authors examined the effect of CrCN coatings obtained by PVD method on mechanical properties and corrosion resistance depending on their C content.
1- After Line 103, you can compare PVD duplex coatings with thermochemical duplex coatings.
https://doi.org/10.1115/1.4047743
2- The data in Table 1 should be given as two digits after the comma.
3- Figure 4a and 4b Name the XRD patterns of the CrN material on the graph.
4- Noise values in Figure 7 tafel charts should be minimized.
5- With the increase in carbon, NbC coatings can be examined, indicating that the crystalline size in the coatings increases and the hardness values improve. https://doi.org/10.1007/s11665-022-07768-3
3- Figure 4a and 4b Name the XRD patterns of the CrN material on the graph.
4- Noise values in Figure 7 tafel charts should be minimized.
5- With the increase in carbon, NbC coatings can be examined, indicating that the crystalline size in the coatings increases and the hardness values improve.
Author Response
We thank the editor and reviewers for their precious remarks and comments. We have taken into account all the highlighted recommendations. The revised manuscript is well enhanced. Here below our responses to the reviewer 2:
In their article, the authors examined the effect of CrCN coatings obtained by PVD method on mechanical properties and corrosion resistance depending on their C content.
We thank the reviewer 2 for the important remarks and comments. The paper was carefully revised and well enhanced.
1- After Line 103, you can compare PVD duplex coatings with thermochemical duplex coatings.
https://doi.org/10.1115/1.4047743
Answer: Thank you for the important publication. This paper is well cited [10] in the revised version.
2- The data in Table 1 should be given as two digits after the comma.
Answer: For light elements measured with EDS, the error is about 5% and the digits after the comma are not really important. For this reason, we find the data presented in this form is more significant.
3- Figure 4a and 4b Name the XRD patterns of the CrN material on the graph.
Answer: Thank you for this remark. It was done in the revised paper.
4- Noise values in Figure 7 tafel charts should be minimized.
Answer: We agree with reviewer 2 but if we did it, some of important shapes/ forms would not be visible in the curve. For that, we preferred to present the figure in this form.
5- With the increase in carbon, NbC coatings can be examined, indicating that the crystalline size in the coatings increases and the hardness values improve. https://doi.org/10.1007/s11665-022-07768-3
Answer: We totally agree, but we apologize for not examining this paper because we do not have access for Springer papers and publications.
Reviewer 4 Report
Dear Authors, I decided for minor revision, because the paper is carefully written, but in fact the chapter related with corrosion should be thoroughly revised.
You can find my remarks in the attachment.
Comments for author File: 
Comments.pdf
Author Response
We would like to thank the reviewer 4 for the precious comments and recommendations. We carefully revised the paper and corrected it. We have taken into account the highlighted remarks and the paper is now well enhanced in this revised version.
Dear Authors, I decided for minor revision, because the paper is carefully written, but in fact the chapter related with corrosion should be thoroughly revised.
The paper entitled ‘A comparative study on the influence of Al2O3-ZnO ALD nanolaminates on the properties of CrCN PVD sputtered coatings with distinctive morphologies and microstructures’ presents a complete study dedicated to the evaluation of coatings.
The results are presented correctly, but I have few questions and remarks for Authors:
- What was the exposed surface of the sample during corrosion measurement? If you used the maximum current of 3 mA for CPP test, the exposed surface should be the same for all samples to have the same conditions for all measurements.
Answer: The exposed surface was 1 cm2. It is determined in our previous publication and cited in the characterization section. Yes, it is the same for all samples.
- The EDS composition in Table 1 is a surface composition of the samples. Therefore, you should have information from similar depth (depending on the parameters used for analysis). You are writing that hybrid coatings have higher oxygen content, because of the ALD oxide layer. Why you did not analyze Al or Zn, to be sure if the oxygen is from the ALD layer?
Answer: Using EDS technique, we measured the elemental composition of the surface. We reduced the accelerating HV to avoid the interaction between the electronic beam and ALD oxide underlayer. We did not detect Al and Zn.
- Figure 1 How was the deposition rate calculated? If you just divided the thickness of coating by the deposition time which was identical for all samples (300 min) the deposition rate is a useless parameter because the same conclusions can be drawn from coating thickness.
Answer: Yes, we just divided the thickness by the deposition time. We prefer to keep this figure which is useful to understand the film growth rate as a function of CH4. We adjusted the deposition time to obtain the same thickness for all coatings.
- Table 1, I do not understand why (C+N)/Cr increased in the case of composite coatings (CrCN-ALD) compared to corresponding CrCN coatings.
Answer: In fact, in the both coatings CrCN-2/ALD and CrCN-4/ALD, the increase of N content balanced with the reduction of Cr percentage results in the increase of this ratio. The little change in composition is maybe due to the substrate on which the coating was deposited, the surface morphology and the competition between the N and Cr atoms during the deposition process.
- It would be interesting to add explanation of Cr2O3 Was the phase created because of the oxygen contamination of argon? In line 407 only reference 13 is reasonable. In reference 45 I did not find information about Cr2O3.
Answer: The formation of Cr2O3 is probably due to the residual oxygen in the chamber during the deposition process and the affinity between Cr and air/ environment after deposition. In the reference 13, in their paper, when they explained the Cr2O3 they cited also the reference 45. For this reason, we cited both references in our paper.
- Chapter 3.2 should have the title ‘Phase composition and microstructure analysis.
Answer: We thank the reviewer 4 for the important remark. We followed the reviewer’s suggestion and modified the title in the revised version.
- Corrosion measurement. This part of the work is unfinished. First of all, you should repeat at least three times each measurement to have statistics in Table 3. Also, your Tafel curves are very noisy. You should explain why. It could be because the sample surface was porous, because of local corrosion (pitting) and because of some experimental problems (with the reference electrode or with the potentiostat settings). I have doubts how it was possible to determine the corrosion potential in the case of such noisy curves. I am also not convinced of the pitting potential in the case of CrCN-2/ALD, CrCN-5/ALD. In fig. 7 I can see the constant growth of current for both samples. General corrosion?
Answer: Yes, we agree with the reviewer 4. All the measurements were repeated three times. In general, this is the form of Tafel curves in TM-nitrides coatings and they become noisier when combined with ALD oxide layers. ALD layers are semiconductors and that make the charge transfer more complicated in the system. The reference electrode and the potentiostat are recent and we don’t think they are the origin of the noise. We performed these experiments at a reasonable scan rate 0.5 mV/s. To improve the visibility, the width of Tafel curves shown in Fig 7 is now reduced from 3 to 2. Since there is a “plateau” that is relative to passive layer formation, even if the current is in constant growth, we interpreted the corrosion as pitting corrosion.
- At least SEM/EDS observations for samples after corrosion tests are recommended.
Answer: We totally agree with the reviewer 4. We tried using an optical microscopy and EDS but there was no important relevant information.
