Corrosion Resistance of High-Entropy Alloys in Plateau Salt-Lake Environments

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Add one sentence in the abstract that includes quantitative results. This will help attract readers and encourage them to read the paper.

High-entropy alloys (HEAs) have been extensively studied worldwide. However, the introduction of this manuscript does not sufficiently address global research trends on HEAs. Therefore, the introduction should be strengthened by incorporating recent international research trends on HEAs. This will improve the readability and provide better context for readers.

Table 1 presents the composition, which corresponds to the Cantor alloy. Therefore, a description of the Cantor alloy should be added to both the introduction and the experimental section.

In the experimental section, the content in Section 2.1 should be reorganized into a table format. The current presentation lacks readability and is difficult to follow.

The experimental section does not specify whether the material is cast or rolled. Therefore, the material condition should be clearly stated.

The caption of Figure 1 should be improved by clearly describing the purpose of the flow chart.

The caption of Figure 3 is written as “Schematic diagram of the microstructure,” which is not appropriate. It should be revised to provide a more accurate and specific description.

All figure captions should be strengthened and elaborated. Revise all captions accordingly.

In Figure 4, the term “pitting pit” is used. This is incorrect terminology. Use either “pitting” or “pit” only. This is a basic issue related to proper terminology usage, and it is recommended to seek guidance from a supervising professor or senior researcher.

This manuscript does not present any analysis of the corrosion cross-section. However, cross-sectional features are included in the schematic diagram. Therefore, relevant references or actual cross-sectional analysis (e.g., images) should be added.

Conclusion 2 should be strengthened. Specifically, explain why Mg and Na do not significantly affect corrosion behavior, and incorporate this discussion into both the discussion and conclusion sections.

Comments on the Quality of English Language

This manuscript is not yet complete. It is recommended to receive guidance from a supervising professor or senior researcher.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In the paper entitled “Corrosion Resistance of High-Entropy Alloys in Plateau Salt-Lake Environments,” there is an interesting topic. However, some corrections and additions can be made.

1. A need for additional reasoning why it is possible to consider a simplified MgCl2 solution as an analog of real brines, taking into account many ions (Cl-, SO4^2−, CO3^2−, Mg^2+, Li^+).
2. It is only one particular high-entropy alloy composition considered: equiatomic CrMnFeCoNi, where each element content amounts to 20 wt.% without comparison to other alloys.
3. It is necessary to explain how changing parameters of testing, such as drying at 40 °C, 30 °C and 80% RH, 30 °C and 20% RH affect the kinetics of corrosion.
4. It is necessary to estimate quantitatively a corrosion pit depth and its size, which is qualitatively presented in the results.
5. In electrochemical investigations, emphasis is placed solely on Rct, even though the need for another parameter like Rp is mentioned.
6. Characterization of corrosion products is conducted using EDX and thus is purely qualitative.
7. No attention is paid to micropores smaller than 1 μm and their role in corrosion initiation.
8. Conclusions do not contain any numbers, which cannot be used in practice.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The paper presents the cyclic wet-dry corrosion behavior of a CrMnFeCoNi high-entropy alloy in simulated salt-lake environments using MgCl₂ and NaCl solutions. The study addresses a relevant and underexplored topic. However, there are crtitical methodological gaps and internal inconsistencies that needs attention. For these reasons, I recommend rejection in its current form, with encouragement for the authors to resubmit a thoroughly revised manuscript for fresh reconsideration.

Below are specific comments and questions that must be addressed by the authors:

1. The authors had identified several chemical species such as Cr(OH)3, Fe(OH)3, Ni(OH)3, etc. from EDS elemental ratios, however, EDS is qualitative and is not capable of distinguishing between hydroxides, oxides, and hydroxy-chlorides. XRD or Raman spectroscopy should be provided, in order to address this fundamental gap in the study. The discussion on the mechanism analysis of corrosion in section 4.2 will not hold if these characterizations are not provided.
2. Another important methodological gap is on section 2.2 and section 3.4. The study relied entirely on the EIS for the electrochemical characterization. These are not enough and a potentiodynamic polarization curves is needed to provide more quantitative data on corrosion rates or to confirm the passivatiaon behavior. 
3. There is also an error and data interpretation with the EIS data. Example, in page 4 line 123, the frequency range is 10^-5 to 10^-2 Hz. Check if this is 10^-2 to 10⁵ Hz.  
4. Also in table 1, it shows an R_ct of 495950 Ω-cm² a day 28 for the MgCl₂ corrosion. However, in the text in lines 31, the Rct reached its max on day 7. This data should be reconciled. 
5. How many samples were tested per condition per time point? Please provide error bars to show the reproducibility of the tests done. 
6. In sections 3.1 and 3.2, the authors should provide pit morphology data to enable a meaningful comparison with the 304SS baseline established in the works of Guo et al. in reference 28.
7. Given the alloy's equal distribution, authors must discuss or comment on the Mn dissolution in the alloy. 
8. Figure 2, provide scale bars and a higher resolution images to clearly distinguish the yellow patches and pit density differences.
9. Figure 3 caption seems incorrect. The images presented are not schematic diagreams but an SEM and EDS elemental maps.
10. Provide a detailed description of all Figures, define/describe all parts especially with multiple images in 1 figure. 
11. Check figure and table numbering. There are errors. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Acceptable it.

Reviewer 3 Report

Comments and Suggestions for Authors

The revised manuscript sufficiently addressed my comments especially on the limitations of the characterization used in the study, hence, I recommend to accept for publication in Metals.