Effect of N₂–H₂ Ratio during Conventional Plasma Nitriding of Intermetallic FeAl40 Alloy on Electrochemical Corrosion Parameters in Sulphuric Acid

Round 1

Reviewer 1 Report

1. Abstract needs the corrosion test environment.
2. Materials and Methods; saturated Ag/AgCl reference electrode can be expressed in (SSC) as like saturated calomel electrode(SCE). Test solution was deaerated or not?
3. Table 1 missed the hardness of 1:9 ratio's specimen.
4. Figure 3; red box needs the magnification or scale.
5. Figure 5; When the nitriding treatment applied, corrosion resistance was reduced except corrosion current density. Please describe the corrosion mechanism for the effect of nitriding, including very high oxygen evolution potential.
6. Table 3; ipass needs the passive potential determined.
7. Conclusion1; Corrosion current density was decreased by the nitriding, but the polarization behavior was totally decreased. Therefore, how can you conclude this behavior?
8. Conclusion2; Increasing N2 fraction, the critical passive potential moved to high value. So, "electrochemical corrosion behavior was not affected" shall be revised.
9. Conclusions should be rewritten after the elucidation of corrosion mechanism by the nitriding.

Author Response

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Reviewer 2 Report

Dear authors,

I enjoyed reading the manuscript because the paper is well-described, and the results are clearly demonstrated. ​

The manuscript, entitled „ Effect of N­­₂ - H₂ Ratio during Conventional Plasma Nitriding of Intermetallic FeAl40 Alloy on Electrochemical Corrosion Parameters in Sulphuric Acid” is relevant to the scope of this journal. It is an interesting study that can provide important information to specialists.

The authors have made a synthesis of the literature that provides an overview of the research evolution in this area.

However, some points need to be addressed before publication of this manuscript. My comments/suggestions are given:

1. Could the authors explain why when the nitrogen levels (fN2) is 0.5 diffusion depth in the nitrided layers has the highest value? (see Figure 4)

2. In my opinion, the XRD data should be presented in the form of recorded spectra, in addition to the results presented in Table 2. Also, a comparison with the existing literature data would be useful and would complete the information.

3. The dot plot representation of the experimental EIS data, at least of the Nyquist plot is indicated.

4. Note that in Figures 9 and 10, in the Bode diagrams the “phase angle” must appear.

5. The error obtained after fitting the EIS experimental data with the proposed electrical equivalent circuits must be specified.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

This work is well addressed. In the Introduction, the background of the work is clearly presented. This work can be accepted after a minor revision.

In Table 4, it is  inappropriate to analyze N element with EDS. Because the atomic number of N is too low.

Author Response

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Author Response File: Author Response.pdf