Experimental Analysis of Reinforcement Rust in Cement under Corrosive Environment
Round 1
Reviewer 1 Report
The authors present a comparitive analysis, using XPS and SEM-EDS, of the surfaces of steel bars which have been exposed to different "intra-concrete" corrosion conditions.
Overall I think this manuscript is of a fairly low quality and I believe that it is not suitable for publication in Coatings. I have a number of major concerns which have led me to this:
1) The authors do not make at all clear what the novel aspect of their work is. They say that work like this has "rarely" been reported and that there are "few" studies which means that I cannot see what is novel about this work?
2) I am unclear as to what new information this work adds to scientific knowledge? The authors conclusions are just a repeat of their discussion and do not make any attempt to say what the wider impact of their results are?
In addition the following minor issues are a cause for concern.
1) The quality of the writing could be improved.
2) The lack of details provided throughout the experimental section would in my opinion make it impossible to repeat the experiment.
3) It could be a lack of clarity, but as described to me it sounds like multiple variables (T and %RH) were also varied when comparing the different corrosion conditions which would mean this wasn't a fair test?
4) I am totally unclear as to what the authors mean by "0 and 5 nm from the surface" for their XPS analysis. Did they ion beam mill it to get a depth profile?
5) In the wide energy range XPS ALL peaks should be identified and an overall elemental quantification should be provided. The fact that Fe appears to be (can't tell without the quantification) such a small component indicates that the surface is still highly contaminated with cement residue and that "brushing it off" was insufficient.
6) The authors state that for each of the samples the Fe 2p peak in the XPS is fitted by 4 (one time 5) peaks whereas in each case it is clear that it is 5 peaks each time? Also only 3 of those peaks are then discussed which means that the % contribution analysis of the different Fe phases is surely wrong?
7) The authors claim that they can see differences in the XPS data on the back of 0.03% shifts in relative % which is just not valid as this would be well within the error of the analysis.
8) The SEM images should be better presented with more legible scale bars.
9) The presentation of the EDS data is very poor to the point that it is impossible to inspect the content.
10) I am generally concerned that there are SIGNIFICANT differences between the eV values ascribed to certain Fe species in the different samples which to my mind raises questions about the reliability of the peak fitting?
11) In some of the XPS data tables the authors seem to be indicating that a given Fe species would have 4 peaks in the Fe 2p spectra when it would only ever have 2 peaks?
Author Response
Thank you for your comments. Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
the title does not quite reflect the novelty of the research. Alternatively, the name can be " Experimental Analysis of Reinforcement Rust in Cement, added acidic water to a mix»;
2) in the keywords you need to add "added acidic water to a mix»;
3) maintenance should be reviewed in terms of increasing the relevance of research and a more detailed analysis of publications, excluding wide ranges of references [1-7] and [17-21];
4) in the section "Materials and methods" for reliability and improvement of the perception of the material, it is desirable to add photos of fittings before and after corrosion. It is necessary to justify the dimensions of the steel rods, the cement bath, and the holding time of the composites before destruction;
5) in the section "Results and discussion", the deciphers of the symbols a, b, c, d should be added to the captions of Figures 2-7, and Figures 3, 5 and 7 should be enlarged (now they are very small);
6) the first item to be added to the output is novelty, i.e. what was first received. In the third conclusion, instead of the trend "... the relative content of iron oxide in the environment is significantly reduced...", indicate the percentage of reduction. The final conclusion should be the prospect of further research;
7) the abstract should also be revised, it should contain the relevance of the research and briefly duplicate the conclusions.
Author Response
Thank you for your comments. Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
The paper presents the results of microstructure tests of reinforcement corrosion products in the chloride environment and those caused by carbonation. The research used X-ray photoelectron spectroscopy (XPS) and scanong electron microscopy combined with energy spectroscopy (SEM-EDX).
Research has shown that rust in a chloride environment consists mainly of Fe3O4 and FeO. In contrast, in a carbonation environment, rust consists mainly of Fe3O4. Fe2O3 was the main rust component in the chloride-carbonation environment. Moreover, it has been shown that the corrosion intensity varies depending on the aggressive factors.
Below are some comments on the work, the inclusion of which should improve the quality of the manuscript:
1. Chapter 1: Lack of clearly formulated purpose and scope of the work.
2. Chapter 2.1, 2.2: The description of tests and research items is weak. I propose to add a few photos: rods and positions. Pictures of the bars before and after corrosion are also necessary. Were the bars ribbed? I think it should be clearly stated which samples were subjected to carbonation, which were subjected to chloride aggression, and which were in a mixed environment.
3. Chapter 3. The results of the research on the structure and composition of rust are described. The description is correct, the only drawback is the lack of an illustration of the place of measurements taking into account the geometry of the concrete. Can the authors consider the obtained results to be correct, since they made single trials? Has the presence of any traces of Fe + been found in the cement? Can a corrosion time prediction be made on the basis of the performed analysis? Are the results consistent with those of other authors? I believe that it is necessary to distinguish between the different corrosive influences (referred to in the abstract): carbonation, chloride corrosion and mixed environment. Chapter 3.1 is only called “3.1. Analysis of micro-corrosion components of steel bars under chloride corrosion "
4. Chapter 4. I believe there is a lack of practical references suggesting directions for further action. Confirmations or contradictions of previous knowledge.
In general, I find the work interesting, it requires supplementing the descriptive and graphic page.
Author Response
Thank you for your comments. Please see the attachment.
Author Response File: Author Response.docx
Reviewer 4 Report
The authors are presenting a work on experimental analysis of reinforcement rust in cement in corrosive environment. The authors employed X-ray photoelectron spectroscopy and scanning electron microscopy/energy spectroscopy for analyzing microstructure characteristics of corrosion products and reinforcement when chloride corrosive environment is introduced.
The study is aimed to show that corrosion degree is higher outside with respect to the inside and rush main composition is Fe3O4.
The study is well structured however most of the figures are barely readable and they should be enlarged for better reading by the readers.
In addition, literature review is quite short and limited and more papers should be included regarding the present topic which has been widely investigated in the recent years.
Author Response
Thank you for your comments. Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors have done a genuinely exceptional job of addressing my concerns and I now believe that this manuscript could be suitable for publication in Coatings subject to the following changes.
1) In my original "Point 6" I asked the authors to explain what they mean by "0 and 5 nm from the surface for their XPS analysis". I am totally satisfied by their explanation buy this needs to be included in the manuscript.
2) For the XPS analysis a full % elemental quantification still needs to be provided to address my concerns with regards to contamination of the surface with cement residue.
3) The authors claim they have addressed my points 10 and 11 with regards to the legibility of the SEM scale bars and the quality of the EDS data. However these have not been adequately addressed and must be before publication.
Reviewer 2 Report
Now the manuscript is clearer. There are no complaints about the quality of the material.
