Corrosion of Stainless Steel by Urea at High Temperature

Round 1

Reviewer 1 Report

This paper should be published after the authors review spelling and grammar mistakes in this paper.  They are not significant but there are several examples such as Section 1. Introduction, 2nd paragraph, first sentence, Most research area on corrosion involving urea is belonging to urea production,..... This is an awkward sentence, try rewriting such as Most research focusing on urea corrosion involves urea production, ..... 

Also the results section should show as a comparison the FTIR spectrum of  pure urea,  biuret, ammelide, ammeline, cyanuric acid, melamine spectra.  This would help the reader see that the authors did indeed identify these products during decomposition. 

Overall this paper can be published with these minor changes. 

Author Response

Dear Reviewer,

thank you for your comments.

English language was checked in the whole text and FTIR spectra of reference materials were added.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear Authors

The manuscript is prepared well, but there are some minor comments (mainly related to figures and their description. 

However, after consideration of these comments, the manuscript can be accepted. 

Regards.  

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

thank you for your comments.

I have improved the description and design of figures.

Author Response File: Author Response.docx

Reviewer 3 Report

This paper attempts to report the Corrosion behavior of stainless steel by urea at high temperature. Both abstract and introduction sections truly described the overall reactions/products related to Urea at the different working temperatures. Therefore, I think this paper can publish in Corrosion and Materials Degradation journal after a minor revision.

The following are some specific comments and points for consideration:

1. The introduction section needs more information regarding corrosion events of stainless steel or other metals or alloys in Urea media.
2. “The overall reaction scheme is”, put the figure number (Figure 1).
3. The size and quality of inserted images in Figure 3 are low. Also, it is difficult to see the urea deposited region, as presented in the orange marked image.
4. What was the size of the crevice gap (length, width, and height)?
5. Figure caption #5 needs more details regarding the SE images. Also, authors can utilize some colored- arrows in order to better present the products and corrosion attacks in the grain boundaries, etc.
6. Dose the rate/intensity of the gas (air) mass flow can influence the intensity of the corroded region by crevice? particularly after 100h cyclic test and considering the oxygen concentration cell.
7. Conclusions section needs more details regarding the effect of the Urea at different temperatures and crevice geometry on localized corrosion attacks.

Author Response

Dear Reviewer,

thank you for your comments.

1. There is no more literature related to this topic, which could give us more understanding about the corrosion of stainless steel by urea.
2. Note for Figure 1 was added to the text.
3. The size of images was increased.
4. The cravice had an average gap of 200 +/- 100 µm.
5. The description to Figure 5 was added.
6. The experiment design was developed at Faurecia Emission Control. The variation of rate/intensity of air flow was not the goal of this paper, thus there is no information about relation of this parameter to corrosion.
7. The text of conclusion was improved.

Author Response File: Author Response.docx