Electrochemical Behavior and Passive Film Properties of Hastelloy C22 Alloy, Laser-Cladding C22 Coating, and Ti–6Al–4V Alloy in Sulfuric Acid Dew-Point Corrosion Environment

Round 1

Reviewer 1 Report

Authors performed the studies on “Electrochemical behaviour and passive film properties of Hastel- 2 loy C22 alloy, laser cladding C22 coating, and Ti–6Al–4V alloy 3 in sulfuric acid dew point corrosion environment”. The results are interesting. Authors are requested to address the following queries.

 

1. The application of Titanium in the FGD environment need to be specified
2. shortage of nickel resources in China leads to the application of titanium alloys with 76 lower performance instead… Please look at the sentence; the cost of Titanium is higher than the Nickel alloys.
3. Section 3, Result should be rewritten as Results
4. Why did the authors are not performed the XRD analysis to evaluate the formation of phases
5. Authors can perform the cross-sectional SEM /EDS mapping.
6. Conclusion should be rewritten as Conclusions
7. The English language needs to be improved overall.

Author Response

Thank you for your advice, please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Avoiding acid dew point corrosion on the low temperature surfaces of FGD and downstream equipment is of great economic interest. Related studies on passivation and corrosion of alloys and laser clad coatings are helpful in selecting appropriate materials.

The authors present the results of various electrochemical investigations in combination with the data of different methods of surface analysis.

The sample preparation and analysis methods are well described. The same applies to the compilation of the measurement results. Tables and figures are clear and contribute to a better understanding. The discussion of the results and the comparison with the literature clearly show the complexity of the topic.

For a better comparison of the microstructure, SEM micrographs of the corroded C22 alloy should be added in Fig. 12 at the same magnification as used for the C22 coatings shown in Fig. 13.

The thickness of a coating is of interest for corrosion resistance. Can you provide information on the thickness of the C22 coatings?

In the discussion, a compact inner layer and a porous outer layer of the passive film formed on the laser cladding C22 coating are described. Here SEM cross-sectional micrographs would be useful and should be added.

Some typos have been identified and should be corrected.
Line 133: Replace dentrite with dendrite.
Line 159: In the dimension, -1 must be written as an exponent.
Lines 160, 161, 164, 274 and 375: Here mse must be written as an index.
Lines 689-698 should be deleted.

Author Response

Thank you for your advice, please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors,

I have read your paper titled "Electrochemical behavior and passive film properties of Hastelloy C22 alloy, laser cladding C22 coating, and Ti–6Al–4V alloy in sulfuric acid dew point corrosion environment". In my opinion the topic is interesting and paper fulfil aims and scope of the Metals journal.

However, I have some suggestions, which may be helpful in improving your work.

Abstract
- I propose to show some of the quantitative results in the abstract

Introduction
- Line 32 "ninety percent of power plants in China" it is a very precise value, I suggest to write -about ninety percent-
- Line 33 "lime and limestone slurry" I my opinion should be -limestone and limestone slurry-
- Line 38 [3-7] I my opinion there are to many references in one bracket. I suggest to extend this part of introduction to avoid citation of 5 work in one bracket
- Line 42 comment like above
- Line 82 I suggest to quote source DOI:10.3390/ma14112745 to confirm the referenced properties
- Line 119 What is the reason of using plural form of noun -powder-?

Materials and specimens
- How many specimens were tested?

Results
This part is clear

Discussion
This part is clear

Conclusions
Generally clear, but I suggest using numbers to describe the differences in the examined properties of the compared materials. If it is possible.

Regards

 

Author Response

Thank you for your advice, please see the attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

With a topics interesting and suitable for Journal Metals and being clearly written in both parts of describing the  used procedures and in the data discussion , the manuscript deserves publication after a revision according to the following:

a)introducing more quantified data after an extensive  treatment of potentiodynamic polarization curves  ( porosity could be computed from polarization resiatance )                               

  b) to better organize the results presentation which now  are in 1 table and 19 figures ; a part of data it will be in the manuscript quality benefit to be included in table;

c) the pores dimension could be indicated with arrows  and evaluated form SEM figures

d) improve discussion about corrosion with evaluation of activation energy using corrosion rate at different temperatures

 

before 

Author Response

Thank you for your advice, please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The author's responses to the comments raised by the reviewer were satisfactory.