Metallurgical Failure Analysis of Closed Water Circuit Containing Molybdate-Based Inhibitor
, Barbara Rivolta 1,*, Riccardo Gerosa 1 and Francesco Iacoviello 2Round 1
Reviewer 1 Report
Memorandum
Subject: Review, March 7, 2023
Metals
Metallurgical failure analysis of closed water circuit containing molybdate-based inhibitor.
Andrea Casaroli1 , Marco Boniardi1 , Barbara Rivolta1* , Riccardo Gerosa1 , Francesco Iacoviello2
Comments:
1. The authors should consider adding a nomenclature to identify parameters and abbreviations used throughout the paper.
2. Figure no. 1 will serve the reader better if it is identified as Figure (a) and Figure (b) instead of using the color as identification.
3. A schematic showing dimensions of the specimens recommended be included in the text.
4. The authors should highlight in some details the experiment tests performed and showing a photo of the experimental setup is very helpful.
5. Labels must be added to some figures pointing out at key point of interests on each image indicating what is being noted in the results and shown.
6. The authors approach to the analytical calculations is not very clear, no analytical data are present nor any comparable results. The authors should elaborate on this by adding additional details with some explanation.
7. The analysis of experimental results section is mainly focused on what is available in the open literature, the authors should consider renaming such section since no analysis seems to be presnt, refrer to No.6 above.
8. The conclusion can be improved, the current statements do not offer a clear concluding remark. The authors should cite what was accomplished and what may have impacted the outcome of the study if any exists. Considering a bullet type statement citing what was found and if anything may have impacted the results would serve the reader better.
Overall, the paper needs more work, upon addressing the above issues, then it can be considered for publication.
Author Response
Please, see the attachments.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors provide a piece of work with experimental evidence of metallurgic failure by means electron microscopies and chemical analysis. The choice of the techniques is appropriate, however, the paper looks overall like a technical report and not like a scientific paper, lacking relevant information and more importantly, interpretation. The paper should provide details on the inhibitor used (mentioned and not explained at all!), as well as on the mechanisms that drive corrosion in their system under study. I do not recommend publication of the paper in the current form.
Below some suggestions to improve the manuscript:
-Pressure written in units ‘barg’, authors should specify that it is gauge pressure
- In Materials and Methods, details of the used instruments should be included, with a detailed explanation of the experimental procedures used
- The authors do not specify it at the beginning of the results, are they analyzing pipes from circuit 2 only or also from circuit 1?
- The authors should describe in detail the inhibitor they are referring to (molybdate-based) and add more information on its structural chemical characterization. How is the inhibitor distributed on the surface, what is its thickness, geometry, homogeneity?
- What it is not clear at all and quite relevant, is the correlation between the inhibitor and the presence of defects on the surface under study.
- Speaking about defects, what is the mechanism of corrosion initiation in a defect?
- The authors mention:
‘In circuit 2 oxygen and the inhibitor are present in the crevice. As said before, it’s possible to state that a stress intensity factor is applied due to the tensile stress induced by the welding operation’.
-What is the role of the inhibitor in stress? The authors should decouple the fact of welding and having an inhibitor on the surface in stress development.
In the literature it has been reported that for metallic alloys with thin film organic inhibitors, a defect in the inhibitor film induces crack-formation due to stress during corrosion (see Frank Uwe Renner et al. Star‐Shaped Crystallographic Cracking of Localized Nanoporous Defects, Advanced Materials 27, 4877 (2015)). Can the authors make an analogy with the type of inhibitor they use?
Author Response
Please see the attachments.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have fully complied with the recommendations proposed.
The paper reads much better. However, one note should be taking into considerations, the conclusion is too long, I recommend on the authors to only list as bullet points the key findings and the issues impacted results if any was encountered.
Reviewer 2 Report
The authors have improved their manuscript by adding essential details about the inhibitors, methodology and more importantly origin and role of cracks on corrosion inhibition. The paper can be published
