Time-Dependent Passivation Performance of Plasma Sprayed FeCrMoCBY Amorphous Coating

Round 1

Reviewer 1 Report

The authors have studied the relationship between passive film growth behavior and passivation time for plasma sprayed Fe48Cr15Mo14C15B6Y2 amorphous coating in borate buffer solution. The work is interesting and the manuscript is well written and well organized. The authors have employed various techniques to report the work, which reflects the strength of the work. I have some suggestions to fully address the work and to improve the manuscript.

1. Line 78 to line 80, the authors mentioned the fabrication of Fe48Cr15Mo14C15B6Y2 was done by gas atomization technique. How were the powders of this amorphous was collected and what was the purity of each component? Detailed procedures for the fabrication of this coating should be mentioned and the source of each component and its purity must be written.

2- Some sentences need corrections; for example, in line 161, "The TEM image and HRTEM micrographs shown in Fig. 4." should be "The TEM image and HRTEM micrographs are shown in Fig. 4.".

3- The resolution of many figures (Figure 5, Figure 6a, Figure 6b, Figure 7, Figure 8, Figure 9, and Figure 10) is low and the figures should be replaced with other clear figures.

4- Cyclic voltammogram part reported in section 3.2.1. is not enough and needs more discussion. 

5- The references are not written as per the format of the coatings journal house style.

The manuscript is written in good English language, only some sentences need to be checked for grammar and typos.

Author Response

1. Line 78 to line 80, the authors mentioned the fabrication of Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂ was done by gas atomization technique. How were the powders of this amorphous was collected and what was the purity of each component? Detailed procedures for the fabrication of this coating should be mentioned and the source of each component and its purity must be written.

We have added the detailed procedures of powder preparation process in section 2.1 based on this suggestion.

2. Some sentences need corrections; for example, in line 161, "The TEM image and HRTEM micrographs shown in Fig. 4." should be "The TEM image and HRTEM micrographs are shown in Fig. 4.".

We have revised this expression.

3. The resolution of many figures (Figure 5, Figure 6a, Figure 6b, Figure 7, Figure 8, Figure 9, and Figure 10) is low and the figures should be replaced with other clear figures.

We have replaced the figures with higher resolution and more clear figures as requested.

4. Cyclic voltammogram part reported in section 3.2.1. is not enough and needs more discussion.

For a better explanation of passivation behavior of this sort of amorphous coating, cyclic polarization curve was graphed instead of cyclic voltammogram part in section 3.2.1. Relevant discussion is also described in this part.

5. The references are not written as per the format of the coatings journal house style.

All the references are reformatted in the form of the coatings journal house style.

Author Response File: Author Response.docx

Reviewer 2 Report

Coatings-2376154
1- In the abstract, you need to focus more on quantitative information, not qualitative ones. In addition, all abbreviations in the whole main text should be defined for the first time. The aforesaid statement should be modified “The extracted passive film thickness d increment with time t conformed … hypothesis”.
2- The novelty and importance of present study should be mentioned in the introduction.
3- The advantages of the plasma sprayed for fabrication of Fe48Cr15Mo14C15B6Y2 amorphous coating compared to the other methods should be stated in the introduction section.
4- There is no image regarding the surface morphology of as-sprayed Fe48Cr15Mo14C15B6Y2 amorphous coating. The coating may include the pin-hole, microcracks/nanocracks, and porosity which have significant effect on the corrosion behavior of as-sprayed Fe48Cr15Mo14C15B6Y2 amorphous coating.
5- How did you prepare samples for assessment with Transmission electron microscopy (TEM).
6- Well-organized discussion should be added regarding corrosion mechanism of as-sprayed Fe48Cr15Mo14C15B6Y2 amorphous coating passivated for various time, combined with recent works and scientific progress in the area. Provide a more in-depth discussion of related previous works.
7- The value of phase angle for as-sprayed coating passivated for 1200, 1800, 3600, 5400 and 7200 s should be stated in the main text.
8- More information regarding the material selection and composition must be given. You have to clarify the reasons for selecting this composition (Fe48Cr15Mo14C15B6Y2)? You have to clarify the reasons for this composition. You have to add a reference for that or explain how you got this composition as optimal ones.
8- Some references about plasma spray might be useful for this article: Journal of Alloys and Compounds 688 (2016) 841-857 and Ceramics International 42 (2016), 357-371. In addition, surprisingly small references to the Coatings in the literature despite the large relevant literature there. This should be improved. There are several important papers in recent literature.

Author Response

1. In the abstract, you need to focus more on quantitative information, not qualitative ones. In addition, all abbreviations in the whole main text should be defined for the first time. The aforesaid statement should be modified “The extracted passive film thickness d increment with time t conformed … hypothesis”.

Thank you for your professional suggestion. We have revised the sentence accordingly.

2. The novelty and importance of present study should be mentioned in the introduction.

The novelty and importance of this work have been underlined in the Introduction part as: This work can provide theoretical guidance for investigation in self-repairing performance, growth model and passivation mechanism involving vacancies transportation process of passive films generated on the surface Fe-based amorphous coatings.

3. The advantages of the plasma sprayed for fabrication of Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂ amorphous coating compared to the other methods should be stated in the introduction section.

We have added relevant description of the advantages of plasma spraying in Introduction part.

4. There is no image regarding the surface morphology of as-sprayed Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂ amorphous coating. The coating may include the pin-hole, microcracks/nanocracks, and porosity which have significant effect on the corrosion behavior of as-sprayed Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂ amorphous coating.

The surface morphology of as-spayed amorphous coating denoted as Fig. 3 has been added in the paper.

5. How did you prepare samples for assessment with Transmission electron microscopy (TEM).

For the preparation of TEM specimen, the as-sprayed amorphous coating was peeled off from Q235 substrate in the shape of a slice, and then burnished to 50 μm by 1500# SiC abrasive paper, and ultimately ion-milled at 4 keV beam energy under Gatan 695 precision ion thinning system. We have added this information into the section 2.2.

6. Well-organized discussion should be added regarding corrosion mechanism of as-sprayed Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂ amorphous coating passivated for various time, combined with recent works and scientific progress in the area. Provide a more in-depth discussion of related previous works.

Thank you for your careful work. Accordingly, the work related to corrosion mechanism for this coating has been described in section 3.4.

7. The value of phase angle for as-sprayed coating passivated for 1200, 1800, 3600, 5400 and 7200 s should be stated in the main text.

We have stated the maximums of phase angles for the coating passivated for various time in the main text as requested.

8. More information regarding the material selection and composition must be given. You have to clarify the reasons for selecting this composition (Fe₄₈Cr₁₅Mo₁₄C₁₅B₆Y₂)? You have to clarify the reasons for this composition. You have to add a reference for that or explain how you got this composition as optimal ones.

This composition of feedstock for plasma spraying was chosen due to its high glass formation ability (GFA) and excellent corrosion resistance as reported in Ref [21].

9. Some references about plasma spray might be useful for this article: Journal of Alloys and Compounds 688 (2016) 841-857 and Ceramics International 42 (2016), 357-371. In addition, surprisingly small references to the Coatings in the literature despite the large relevant literature there. This should be improved. There are several important papers in recent literature.

Thank you for your advice. We have added Ceramics International 42 (2016) as Ref [6] in this paper. In addition, Ref [2], [7] [61] have been cited from Coatings journal.

Author Response File: Author Response.docx

Reviewer 3 Report

Dear authors

The paper is very interesting with commendable work

I send you my comments

Best regards

Comments for author File: Comments.pdf

Author Response

1. Abstract

It is correct and adequate, but in line 19 I would suggest putting the d and t in italics or between parentheses to indicate that they are variables.

We have revised d and t in italics as suggested.

2. Experimental
   • Was the material produced by the authors themselves or is it a commercial product or was it produced by third parties? In that case they should be named.

The powder is a commercial product produced by Beijing ZJLG Amorphous Technology CO., Ltd. Necessary information has been added in section 2.1.

• In the electrochemical measurements, how was the sample isolated so that the exposure was 1 cm²?

The samples were machined into 10×10×8 mm³ by wire-electrode cutting. We have provided this information in section 2.3 as suggested.

• Was the sample washed with water or acetone after polishing?

The sample was cleaned with acetone after polishing and we have added relevant information in section 2.3.

3. Results and Discussion
   • The format of the equations must be homogenized.

The format of all equations has been homogenized as requested.

4. Conclusions
   • The conclusions require an introductory sentence to guide the four findings that are indicated.

We have added an introductory sentence in this part. Thank you for your useful advice.

Author Response File: Author Response.docx

Reviewer 4 Report

The paper describes with different methods the passivation process on Plasma sprayed coatings.

All data are clear intepreted and the final model secribes the passivation process.

Accepted.

Author Response

Thank you for your kindness.

Author Response File: Author Response.docx